16561631 has 4 divisors (see below), whose sum is σ = 16590912. Its totient is φ = 16532352.

The previous prime is 16561627. The next prime is 16561661. The reversal of 16561631 is 13616561.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 16561631 - 2² = 16561627 is a prime.

It is a super-2 number, since 2×16561631² = 548575242760322, 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 = 16561594 and 16561603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561661) 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, 13775 + ... + 14928.

It is an arithmetic number, because the mean of its divisors is an integer number (4147728).

Almost surely, 2^16561631 is an apocalyptic number.

16561631 is a deficient number, since it is larger than the sum of its proper divisors (29281).

16561631 is an equidigital number, since it uses as much as digits as its factorization.

16561631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29280.

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

The square root of 16561631 is about 4069.5983831332. The cubic root of 16561631 is about 254.8987474469.

The spelling of 16561631 in words is "sixteen million, five hundred sixty-one thousand, six hundred thirty-one".