21802531 has 2 divisors, whose sum is σ = 21802532. Its totient is φ = 21802530.

The previous prime is 21802513. The next prime is 21802541. The reversal of 21802531 is 13520812.

Together with previous prime (21802513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21802531 - 2¹¹ = 21800483 is a prime.

It is a super-2 number, since 2×21802531² = 950700716011922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21802541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10901265 + 10901266.

It is an arithmetic number, because the mean of its divisors is an integer number (10901266).

Almost surely, 2^21802531 is an apocalyptic number.

21802531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21802531 is an equidigital number, since it uses as much as digits as its factorization.

21802531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21802531 is about 4669.3180444258. The cubic root of 21802531 is about 279.3630547237.

The spelling of 21802531 in words is "twenty-one million, eight hundred two thousand, five hundred thirty-one".