21680402 has 4 divisors (see below), whose sum is σ = 32520606. Its totient is φ = 10840200.

The previous prime is 21680381. The next prime is 21680413. The reversal of 21680402 is 20408612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20511841 + 1168561 = 4529^2 + 1081^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5420099 + ... + 5420102.

Almost surely, 2^21680402 is an apocalyptic number.

21680402 is a deficient number, since it is larger than the sum of its proper divisors (10840204).

21680402 is a wasteful number, since it uses less digits than its factorization.

21680402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10840203.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21680402 is about 4656.2218589754. The cubic root of 21680402 is about 278.8404512513.

The spelling of 21680402 in words is "twenty-one million, six hundred eighty thousand, four hundred two".