21025431 has 12 divisors (see below), whose sum is σ = 34708752. Its totient is φ = 12014496.

The previous prime is 21025423. The next prime is 21025439. The reversal of 21025431 is 13452012.

21025431 is a `hidden beast` number, since 210 + 25 + 431 = 666.

It is an interprime number because it is at equal distance from previous prime (21025423) and next prime (21025439).

It is not a de Polignac number, because 21025431 - 2³ = 21025423 is a prime.

It is a super-2 number, since 2×21025431² = 884137497471522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21025439) 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 11 ways as a sum of consecutive naturals, for example, 166806 + ... + 166931.

It is an arithmetic number, because the mean of its divisors is an integer number (2892396).

Almost surely, 2^21025431 is an apocalyptic number.

21025431 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21025431 is a deficient number, since it is larger than the sum of its proper divisors (13683321).

21025431 is a wasteful number, since it uses less digits than its factorization.

21025431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333750 (or 333747 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21025431 is about 4585.3496049920. The cubic root of 21025431 is about 276.0037412851.

Adding to 21025431 its reverse (13452012), we get a palindrome (34477443).

The spelling of 21025431 in words is "twenty-one million, twenty-five thousand, four hundred thirty-one".