20531231 has 16 divisors (see below), whose sum is σ = 24023040. Its totient is φ = 17184960.

The previous prime is 20531219. The next prime is 20531243. The reversal of 20531231 is 13213502.

It is an interprime number because it is at equal distance from previous prime (20531219) and next prime (20531243).

It is a cyclic number.

It is not a de Polignac number, because 20531231 - 2¹⁸ = 20269087 is a prime.

It is a super-2 number, since 2×20531231² = 843062892750722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20531431) 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, 75626 + ... + 75896.

It is an arithmetic number, because the mean of its divisors is an integer number (1501440).

Almost surely, 2^20531231 is an apocalyptic number.

20531231 is a deficient number, since it is larger than the sum of its proper divisors (3491809).

20531231 is a wasteful number, since it uses less digits than its factorization.

20531231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 494.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 20531231 is about 4531.1401434959. The cubic root of 20531231 is about 273.8240963425.

Adding to 20531231 its reverse (13213502), we get a palindrome (33744733).

The spelling of 20531231 in words is "twenty million, five hundred thirty-one thousand, two hundred thirty-one".