20818631 has 4 divisors (see below), whose sum is σ = 20830272. Its totient is φ = 20806992.

The previous prime is 20818621. The next prime is 20818643. The reversal of 20818631 is 13681802.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20818631 - 2¹⁰ = 20817607 is a prime.

It is a super-2 number, since 2×20818631² = 866830793428322, 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 = 20818594 and 20818603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20818601) 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, 2510 + ... + 6923.

It is an arithmetic number, because the mean of its divisors is an integer number (5207568).

Almost surely, 2^20818631 is an apocalyptic number.

20818631 is a deficient number, since it is larger than the sum of its proper divisors (11641).

20818631 is an equidigital number, since it uses as much as digits as its factorization.

20818631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11640.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 20818631 is about 4562.7438017053. The cubic root of 20818631 is about 275.0958607954.

The spelling of 20818631 in words is "twenty million, eight hundred eighteen thousand, six hundred thirty-one".