21415531 has 2 divisors, whose sum is σ = 21415532. Its totient is φ = 21415530.

The previous prime is 21415519. The next prime is 21415547. The reversal of 21415531 is 13551412.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21415531 - 2¹⁵ = 21382763 is a prime.

It is a super-2 number, since 2×21415531² = 917249936023922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21415561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10707765 + 10707766.

It is an arithmetic number, because the mean of its divisors is an integer number (10707766).

Almost surely, 2^21415531 is an apocalyptic number.

21415531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21415531 is an equidigital number, since it uses as much as digits as its factorization.

21415531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 600, while the sum is 22.

The square root of 21415531 is about 4627.6917572371. The cubic root of 21415531 is about 277.7002574734.

Adding to 21415531 its reverse (13551412), we get a palindrome (34966943).

The spelling of 21415531 in words is "twenty-one million, four hundred fifteen thousand, five hundred thirty-one".