161642521 has 4 divisors (see below), whose sum is σ = 163243044. Its totient is φ = 160042000.

The previous prime is 161642479. The next prime is 161642543. The reversal of 161642521 is 125246161.

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 159668496 + 1974025 = 12636^2 + 1405^2 .

It is a cyclic number.

It is not a de Polignac number, because 161642521 - 2²³ = 153253913 is a prime.

It is a super-2 number, since 2×161642521² = 52256609190470882, which contains 22 as substring.

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 161642521.

It is not an unprimeable number, because it can be changed into a prime (161642021) 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, 800110 + ... + 800311.

It is an arithmetic number, because the mean of its divisors is an integer number (40810761).

Almost surely, 2^161642521 is an apocalyptic number.

It is an amenable number.

161642521 is a deficient number, since it is larger than the sum of its proper divisors (1600523).

161642521 is a wasteful number, since it uses less digits than its factorization.

161642521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1600522.

The product of its digits is 2880, while the sum is 28.

The square root of 161642521 is about 12713.8712043185. The cubic root of 161642521 is about 544.7349057252.

Adding to 161642521 its reverse (125246161), we get a palindrome (286888682).

The spelling of 161642521 in words is "one hundred sixty-one million, six hundred forty-two thousand, five hundred twenty-one".