20561631 has 4 divisors (see below), whose sum is σ = 27415512. Its totient is φ = 13707752.

The previous prime is 20561621. The next prime is 20561633. The reversal of 20561631 is 13616502.

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 20561631 - 2⁵ = 20561599 is a prime.

It is a super-2 number, since 2×20561631² = 845561338760322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20561633) 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, 3426936 + ... + 3426941.

It is an arithmetic number, because the mean of its divisors is an integer number (6853878).

Almost surely, 2^20561631 is an apocalyptic number.

20561631 is a deficient number, since it is larger than the sum of its proper divisors (6853881).

20561631 is an equidigital number, since it uses as much as digits as its factorization.

20561631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6853880.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 20561631 is about 4534.4934667502. The cubic root of 20561631 is about 273.9591775011.

The spelling of 20561631 in words is "twenty million, five hundred sixty-one thousand, six hundred thirty-one".