21513663 has 24 divisors (see below), whose sum is σ = 31917600. Its totient is φ = 13959360.

The previous prime is 21513649. The next prime is 21513689. The reversal of 21513663 is 36631512.

It is not a de Polignac number, because 21513663 - 2⁴ = 21513647 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513623) 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 in 23 ways as a sum of consecutive naturals, for example, 81670 + ... + 81932.

It is an arithmetic number, because the mean of its divisors is an integer number (1329900).

Almost surely, 2^21513663 is an apocalyptic number.

21513663 is a deficient number, since it is larger than the sum of its proper divisors (10403937).

21513663 is a wasteful number, since it uses less digits than its factorization.

21513663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 479 (or 476 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 21513663 is about 4638.2823329332. The cubic root of 21513663 is about 278.1237781876.

The spelling of 21513663 in words is "twenty-one million, five hundred thirteen thousand, six hundred sixty-three".