181916147821 has 4 divisors (see below), whose sum is σ = 181918808092. Its totient is φ = 181913487552.

The previous prime is 181916147797. The next prime is 181916147857. The reversal of 181916147821 is 128741619181.

It is a happy number.

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 97790045796 + 84126102025 = 312714^2 + 290045^2 .

It is a cyclic number.

It is not a de Polignac number, because 181916147821 - 2⁵ = 181916147789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181916147221) 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, 1224780 + ... + 1365253.

It is an arithmetic number, because the mean of its divisors is an integer number (45479702023).

Almost surely, 2^181916147821 is an apocalyptic number.

It is an amenable number.

181916147821 is a deficient number, since it is larger than the sum of its proper divisors (2660271).

181916147821 is an equidigital number, since it uses as much as digits as its factorization.

181916147821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2660270.

The product of its digits is 193536, while the sum is 49.

The spelling of 181916147821 in words is "one hundred eighty-one billion, nine hundred sixteen million, one hundred forty-seven thousand, eight hundred twenty-one".