21723513 has 12 divisors (see below), whose sum is σ = 33693840. Its totient is φ = 12413352.

The previous prime is 21723469. The next prime is 21723539. The reversal of 21723513 is 31532712.

It is not a de Polignac number, because 21723513 - 2⁸ = 21723257 is a prime.

It is a super-2 number, since 2×21723513² = 943822034122338, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21723553) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 73743 + ... + 74036.

It is an arithmetic number, because the mean of its divisors is an integer number (2807820).

Almost surely, 2^21723513 is an apocalyptic number.

It is an amenable number.

21723513 is a deficient number, since it is larger than the sum of its proper divisors (11970327).

21723513 is a wasteful number, since it uses less digits than its factorization.

21723513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 147796 (or 147789 counting only the distinct ones).

The product of its digits is 1260, while the sum is 24.

The square root of 21723513 is about 4660.8489570034. The cubic root of 21723513 is about 279.0251515718.

The spelling of 21723513 in words is "twenty-one million, seven hundred twenty-three thousand, five hundred thirteen".