21352531 has 2 divisors, whose sum is σ = 21352532. Its totient is φ = 21352530.

The previous prime is 21352517. The next prime is 21352543. The reversal of 21352531 is 13525312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21352531 - 2⁷ = 21352403 is a prime.

It is a super-2 number, since 2×21352531² = 911861160211922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21352571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10676265 + 10676266.

It is an arithmetic number, because the mean of its divisors is an integer number (10676266).

Almost surely, 2^21352531 is an apocalyptic number.

21352531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21352531 is an equidigital number, since it uses as much as digits as its factorization.

21352531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 900, while the sum is 22.

The square root of 21352531 is about 4620.8798945655. The cubic root of 21352531 is about 277.4276780392.

Adding to 21352531 its reverse (13525312), we get a palindrome (34877843).

The spelling of 21352531 in words is "twenty-one million, three hundred fifty-two thousand, five hundred thirty-one".