21532731 has 8 divisors (see below), whose sum is σ = 31320384. Its totient is φ = 13050120.

The previous prime is 21532717. The next prime is 21532733. The reversal of 21532731 is 13723512.

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

It is not a de Polignac number, because 21532731 - 2⁷ = 21532603 is a prime.

It is a super-2 number, since 2×21532731² = 927317008636722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21532733) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 326221 + ... + 326286.

It is an arithmetic number, because the mean of its divisors is an integer number (3915048).

Almost surely, 2^21532731 is an apocalyptic number.

21532731 is a deficient number, since it is larger than the sum of its proper divisors (9787653).

21532731 is a wasteful number, since it uses less digits than its factorization.

21532731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 652521.

The product of its digits is 1260, while the sum is 24.

The square root of 21532731 is about 4640.3373799757. The cubic root of 21532731 is about 278.2059228566.

It can be divided in two parts, 2153 and 2731, that added together give a palindrome (4884).

The spelling of 21532731 in words is "twenty-one million, five hundred thirty-two thousand, seven hundred thirty-one".