20631261 has 16 divisors (see below), whose sum is σ = 32108544. Its totient is φ = 11537904.

The previous prime is 20631229. The next prime is 20631263. The reversal of 20631261 is 16213602.

It is a happy number.

It is not a de Polignac number, because 20631261 - 2⁵ = 20631229 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20631263) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9465 + ... + 11438.

It is an arithmetic number, because the mean of its divisors is an integer number (2006784).

Almost surely, 2^20631261 is an apocalyptic number.

20631261 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20631261 is a deficient number, since it is larger than the sum of its proper divisors (11477283).

20631261 is a wasteful number, since it uses less digits than its factorization.

20631261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20960.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 20631261 is about 4542.1647922549. The cubic root of 20631261 is about 274.2680746112.

Adding to 20631261 its reverse (16213602), we get a palindrome (36844863).

The spelling of 20631261 in words is "twenty million, six hundred thirty-one thousand, two hundred sixty-one".