21513709 has 8 divisors (see below), whose sum is σ = 24615360. Its totient is φ = 18419136.

The previous prime is 21513697. The next prime is 21513749. The reversal of 21513709 is 90731512.

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

It is a cyclic number.

It is not a de Polignac number, because 21513709 - 2⁹ = 21513197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513749) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9882 + ... + 11860.

It is an arithmetic number, because the mean of its divisors is an integer number (3076920).

Almost surely, 2^21513709 is an apocalyptic number.

It is an amenable number.

21513709 is a deficient number, since it is larger than the sum of its proper divisors (3101651).

21513709 is a wasteful number, since it uses less digits than its factorization.

21513709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3539.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21513709 is about 4638.2872916627. The cubic root of 21513709 is about 278.1239764134.

It can be divided in two parts, 21513 and 709, that added together give a palindrome (22222).

The spelling of 21513709 in words is "twenty-one million, five hundred thirteen thousand, seven hundred nine".