170551981 has 4 divisors (see below), whose sum is σ = 175161532. Its totient is φ = 165942432.

The previous prime is 170551967. The next prime is 170552003. The reversal of 170551981 is 189155071.

170551981 = 9234² + 9235².

170551981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 85266756 + 85285225 = 9234^2 + 9235^2 .

It is a cyclic number.

It is not a de Polignac number, because 170551981 - 2⁷ = 170551853 is a prime.

It is a super-2 number, since 2×170551981² = 58175956446048722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 4609513 = 170551981 / (1 + 7 + 0 + 5 + 5 + 1 + 9 + 8 + 1).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 170551981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (170551921) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2304720 + ... + 2304793.

It is an arithmetic number, because the mean of its divisors is an integer number (43790383).

Almost surely, 2^170551981 is an apocalyptic number.

170551981 is the 9235-th centered square number.

It is an amenable number.

170551981 is a deficient number, since it is larger than the sum of its proper divisors (4609551).

170551981 is an equidigital number, since it uses as much as digits as its factorization.

170551981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4609550.

The product of its (nonzero) digits is 12600, while the sum is 37.

The square root of 170551981 is about 13059.5551608774. Note that the first 3 decimals coincide. The cubic root of 170551981 is about 554.5647438267.

The spelling of 170551981 in words is "one hundred seventy million, five hundred fifty-one thousand, nine hundred eighty-one".