21252531 has 8 divisors (see below), whose sum is σ = 28501200. Its totient is φ = 14086112.

The previous prime is 21252509. The next prime is 21252547. The reversal of 21252531 is 13525212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21252531 - 2⁷ = 21252403 is a prime.

It is a super-2 number, since 2×21252531² = 903340147811922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21252498 and 21252507.

It is not an unprimeable number, because it can be changed into a prime (21252551) 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 7 ways as a sum of consecutive naturals, for example, 19956 + ... + 20993.

It is an arithmetic number, because the mean of its divisors is an integer number (3562650).

Almost surely, 2^21252531 is an apocalyptic number.

21252531 is a deficient number, since it is larger than the sum of its proper divisors (7248669).

21252531 is a wasteful number, since it uses less digits than its factorization.

21252531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41125.

The product of its digits is 600, while the sum is 21.

The square root of 21252531 is about 4610.0467459669. The cubic root of 21252531 is about 276.9939091659.

Adding to 21252531 its reverse (13525212), we get a palindrome (34777743).

It can be divided in two parts, 2125 and 2531, that added together give a triangular number (4656 = T₉₆).

The spelling of 21252531 in words is "twenty-one million, two hundred fifty-two thousand, five hundred thirty-one".