21510539 has 2 divisors, whose sum is σ = 21510540. Its totient is φ = 21510538.

The previous prime is 21510521. The next prime is 21510553. The reversal of 21510539 is 93501512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21510539 - 2²⁰ = 20461963 is a prime.

It is not a weakly prime, because it can be changed into another prime (21512539) 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, 10755269 + 10755270.

It is an arithmetic number, because the mean of its divisors is an integer number (10755270).

Almost surely, 2^21510539 is an apocalyptic number.

21510539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21510539 is an equidigital number, since it uses as much as digits as its factorization.

21510539 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 21510539 is about 4637.9455581108. The cubic root of 21510539 is about 278.1103154137.

The spelling of 21510539 in words is "twenty-one million, five hundred ten thousand, five hundred thirty-nine".