21431025 has 72 divisors (see below), whose sum is σ = 47895744. Its totient is φ = 8899200.

The previous prime is 21431023. The next prime is 21431057. The reversal of 21431025 is 52013412.

It is not a de Polignac number, because 21431025 - 2¹ = 21431023 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21430989 and 21431007.

It is not an unprimeable number, because it can be changed into a prime (21431023) 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 71 ways as a sum of consecutive naturals, for example, 16707 + ... + 17943.

Almost surely, 2^21431025 is an apocalyptic number.

21431025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21431025 is an abundant number, since it is smaller than the sum of its proper divisors (26464719).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21431025 is a wasteful number, since it uses less digits than its factorization.

21431025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1271 (or 1263 counting only the distinct ones).

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

The square root of 21431025 is about 4629.3655072807. The cubic root of 21431025 is about 277.7672127834.

Adding to 21431025 its reverse (52013412), we get a palindrome (73444437).

The spelling of 21431025 in words is "twenty-one million, four hundred thirty-one thousand, twenty-five".