21513021 has 8 divisors (see below), whose sum is σ = 29459424. Its totient is φ = 13954320.

The previous prime is 21513013. The next prime is 21513031. The reversal of 21513021 is 12031512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21513021 - 2³ = 21513013 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513001) 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 in 7 ways as a sum of consecutive naturals, for example, 96795 + ... + 97016.

It is an arithmetic number, because the mean of its divisors is an integer number (3682428).

Almost surely, 2^21513021 is an apocalyptic number.

It is an amenable number.

21513021 is a deficient number, since it is larger than the sum of its proper divisors (7946403).

21513021 is a wasteful number, since it uses less digits than its factorization.

21513021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193851.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21513021 is about 4638.2131257630. The cubic root of 21513021 is about 278.1210116164.

Adding to 21513021 its reverse (12031512), we get a palindrome (33544533).

The spelling of 21513021 in words is "twenty-one million, five hundred thirteen thousand, twenty-one".