21292531 has 4 divisors (see below), whose sum is σ = 22930432. Its totient is φ = 19654632.

The previous prime is 21292519. The next prime is 21292541. The reversal of 21292531 is 13529212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21292531 - 2¹³ = 21284339 is a prime.

It is a super-2 number, since 2×21292531² = 906743752771922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21292496 and 21292505.

It is not an unprimeable number, because it can be changed into a prime (21292541) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 818931 + ... + 818956.

It is an arithmetic number, because the mean of its divisors is an integer number (5732608).

Almost surely, 2^21292531 is an apocalyptic number.

21292531 is a deficient number, since it is larger than the sum of its proper divisors (1637901).

21292531 is a wasteful number, since it uses less digits than its factorization.

21292531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1637900.

The product of its digits is 1080, while the sum is 25.

The square root of 21292531 is about 4614.3830573545. The cubic root of 21292531 is about 277.1675796564.

The spelling of 21292531 in words is "twenty-one million, two hundred ninety-two thousand, five hundred thirty-one".