21668628 has 36 divisors (see below), whose sum is σ = 52271520. Its totient is φ = 6986160.

The previous prime is 21668609. The next prime is 21668629. The reversal of 21668628 is 82686612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668629) 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, 10593 + ... + 12471.

Almost surely, 2^21668628 is an apocalyptic number.

It is an amenable number.

21668628 is an abundant number, since it is smaller than the sum of its proper divisors (30602892).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21668628 is a wasteful number, since it uses less digits than its factorization.

21668628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1948 (or 1915 counting only the distinct ones).

The product of its digits is 55296, while the sum is 39.

The square root of 21668628 is about 4654.9573574846. The cubic root of 21668628 is about 278.7899653798.

The spelling of 21668628 in words is "twenty-one million, six hundred sixty-eight thousand, six hundred twenty-eight".