21413531 has 2 divisors, whose sum is σ = 21413532. Its totient is φ = 21413530.

The previous prime is 21413479. The next prime is 21413533. The reversal of 21413531 is 13531412.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21413531 is a prime.

It is a super-2 number, since 2×21413531² = 917078619775922, which contains 22 as substring.

Together with 21413533, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21413533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10706765 + 10706766.

It is an arithmetic number, because the mean of its divisors is an integer number (10706766).

Almost surely, 2^21413531 is an apocalyptic number.

21413531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21413531 is an equidigital number, since it uses as much as digits as its factorization.

21413531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 360, while the sum is 20.

The square root of 21413531 is about 4627.4756617404. The cubic root of 21413531 is about 277.6916123798.

Adding to 21413531 its reverse (13531412), we get a palindrome (34944943).

The spelling of 21413531 in words is "twenty-one million, four hundred thirteen thousand, five hundred thirty-one".