161637521 has 4 divisors (see below), whose sum is σ = 164377200. Its totient is φ = 158897844.

The previous prime is 161637451. The next prime is 161637523. The reversal of 161637521 is 125736161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 161637521 - 2²² = 157443217 is a prime.

It is a super-2 number, since 2×161637521² = 52253376390050882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161637523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1369751 + ... + 1369868.

It is an arithmetic number, because the mean of its divisors is an integer number (41094300).

Almost surely, 2^161637521 is an apocalyptic number.

It is an amenable number.

161637521 is a deficient number, since it is larger than the sum of its proper divisors (2739679).

161637521 is an equidigital number, since it uses as much as digits as its factorization.

161637521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2739678.

The product of its digits is 7560, while the sum is 32.

The square root of 161637521 is about 12713.6745671737. The cubic root of 161637521 is about 544.7292890046.

The spelling of 161637521 in words is "one hundred sixty-one million, six hundred thirty-seven thousand, five hundred twenty-one".