21163531 has 2 divisors, whose sum is σ = 21163532. Its totient is φ = 21163530.

The previous prime is 21163507. The next prime is 21163543. The reversal of 21163531 is 13536112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21163531 - 2⁷ = 21163403 is a prime.

It is a super-2 number, since 2×21163531² = 895790088775922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21163561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10581765 + 10581766.

It is an arithmetic number, because the mean of its divisors is an integer number (10581766).

Almost surely, 2^21163531 is an apocalyptic number.

21163531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21163531 is an equidigital number, since it uses as much as digits as its factorization.

21163531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 540, while the sum is 22.

The square root of 21163531 is about 4600.3837883377. The cubic root of 21163531 is about 276.6067089956.

Adding to 21163531 its reverse (13536112), we get a palindrome (34699643).

The spelling of 21163531 in words is "twenty-one million, one hundred sixty-three thousand, five hundred thirty-one".