15661631 has 4 divisors (see below), whose sum is σ = 16043664. Its totient is φ = 15279600.

The previous prime is 15661601. The next prime is 15661637. The reversal of 15661631 is 13616651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13616651 = 1277 ⋅10663.

It is a cyclic number.

It is not a de Polignac number, because 15661631 - 2²² = 11467327 is a prime.

It is a super-2 number, since 2×15661631² = 490573371160322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15661594 and 15661603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15661637) 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, 190955 + ... + 191036.

It is an arithmetic number, because the mean of its divisors is an integer number (4010916).

Almost surely, 2^15661631 is an apocalyptic number.

15661631 is a deficient number, since it is larger than the sum of its proper divisors (382033).

15661631 is an equidigital number, since it uses as much as digits as its factorization.

15661631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 382032.

The product of its digits is 3240, while the sum is 29.

The square root of 15661631 is about 3957.4778584346. The cubic root of 15661631 is about 250.1952128614.

The spelling of 15661631 in words is "fifteen million, six hundred sixty-one thousand, six hundred thirty-one".