20390531 has 24 divisors (see below), whose sum is σ = 25560864. Its totient is φ = 15874560.

The previous prime is 20390483. The next prime is 20390549. The reversal of 20390531 is 13509302.

It is a happy number.

It is not a de Polignac number, because 20390531 - 2¹⁸ = 20128387 is a prime.

It is a super-2 number, since 2×20390531² = 831547508923922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20390497 and 20390506.

It is not an unprimeable number, because it can be changed into a prime (20390431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 334241 + ... + 334301.

It is an arithmetic number, because the mean of its divisors is an integer number (1065036).

Almost surely, 2^20390531 is an apocalyptic number.

20390531 is a deficient number, since it is larger than the sum of its proper divisors (5170333).

20390531 is an equidigital number, since it uses as much as digits as its factorization.

20390531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191 (or 138 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 23.

The square root of 20390531 is about 4515.5875586683. The cubic root of 20390531 is about 273.1971588531.

Adding to 20390531 its reverse (13509302), we get a palindrome (33899833).

The spelling of 20390531 in words is "twenty million, three hundred ninety thousand, five hundred thirty-one".