21680507 has 4 divisors (see below), whose sum is σ = 21691296. Its totient is φ = 21669720.

The previous prime is 21680497. The next prime is 21680587. The reversal of 21680507 is 70508612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21680507 - 2⁶ = 21680443 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21680507.

It is not an unprimeable number, because it can be changed into a prime (21680587) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1388 + ... + 6729.

It is an arithmetic number, because the mean of its divisors is an integer number (5422824).

Almost surely, 2^21680507 is an apocalyptic number.

21680507 is a deficient number, since it is larger than the sum of its proper divisors (10789).

21680507 is an equidigital number, since it uses as much as digits as its factorization.

21680507 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10788.

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 21680507 is about 4656.2331341976. The cubic root of 21680507 is about 278.8409013998.

The spelling of 21680507 in words is "twenty-one million, six hundred eighty thousand, five hundred seven".