1601981 has 4 divisors (see below), whose sum is σ = 1607964. Its totient is φ = 1596000.

The previous prime is 1601969. The next prime is 1602011. The reversal of 1601981 is 1891061.

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 1229881 + 372100 = 1109^2 + 610^2 .

It is a cyclic number.

It is not a de Polignac number, because 1601981 - 2¹⁰ = 1600957 is a prime.

It is a super-3 number, since 3×1601981³ = 12333698774120877423, which contains 333 as substring. Note that it is a super-d number also for d = 2.

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 1601981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1601381) 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, 2570 + ... + 3131.

It is an arithmetic number, because the mean of its divisors is an integer number (401991).

2^1601981 is an apocalyptic number.

It is an amenable number.

1601981 is a deficient number, since it is larger than the sum of its proper divisors (5983).

1601981 is an equidigital number, since it uses as much as digits as its factorization.

1601981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5982.

The product of its (nonzero) digits is 432, while the sum is 26.

The square root of 1601981 is about 1265.6938808417. The cubic root of 1601981 is about 117.0089602800.

The spelling of 1601981 in words is "one million, six hundred one thousand, nine hundred eighty-one".