21548531 has 2 divisors, whose sum is σ = 21548532. Its totient is φ = 21548530.

The previous prime is 21548507. The next prime is 21548551. The reversal of 21548531 is 13584512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21548531 - 2¹⁸ = 21286387 is a prime.

It is a super-2 number, since 2×21548531² = 928678376515922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21548494 and 21548503.

It is not a weakly prime, because it can be changed into another prime (21548551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10774265 + 10774266.

It is an arithmetic number, because the mean of its divisors is an integer number (10774266).

Almost surely, 2^21548531 is an apocalyptic number.

21548531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21548531 is an equidigital number, since it uses as much as digits as its factorization.

21548531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4800, while the sum is 29.

The square root of 21548531 is about 4642.0395302065. The cubic root of 21548531 is about 278.2739522965.

The spelling of 21548531 in words is "twenty-one million, five hundred forty-eight thousand, five hundred thirty-one".