21531275 has 12 divisors (see below), whose sum is σ = 28104600. Its totient is φ = 16318080.

The previous prime is 21531269. The next prime is 21531317. The reversal of 21531275 is 57213512.

It is not a de Polignac number, because 21531275 - 2¹⁰ = 21530251 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22190 + ... + 23139.

It is an arithmetic number, because the mean of its divisors is an integer number (2342050).

Almost surely, 2^21531275 is an apocalyptic number.

21531275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21531275 is a deficient number, since it is larger than the sum of its proper divisors (6573325).

21531275 is a wasteful number, since it uses less digits than its factorization.

21531275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45358 (or 45353 counting only the distinct ones).

The product of its digits is 2100, while the sum is 26.

The square root of 21531275 is about 4640.1804921792. The cubic root of 21531275 is about 278.1996521401.

Adding to 21531275 its reverse (57213512), we get a palindrome (78744787).

The spelling of 21531275 in words is "twenty-one million, five hundred thirty-one thousand, two hundred seventy-five".