21513587 has 2 divisors, whose sum is σ = 21513588. Its totient is φ = 21513586.

The previous prime is 21513559. The next prime is 21513593. The reversal of 21513587 is 78531512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21513587 - 2⁶ = 21513523 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21513787) 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, 10756793 + 10756794.

It is an arithmetic number, because the mean of its divisors is an integer number (10756794).

Almost surely, 2^21513587 is an apocalyptic number.

21513587 is a deficient number, since it is larger than the sum of its proper divisors (1).

21513587 is an equidigital number, since it uses as much as digits as its factorization.

21513587 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8400, while the sum is 32.

The square root of 21513587 is about 4638.2741402379. The cubic root of 21513587 is about 278.1234506836.

The spelling of 21513587 in words is "twenty-one million, five hundred thirteen thousand, five hundred eighty-seven".