21405668 has 12 divisors (see below), whose sum is σ = 37537920. Its totient is φ = 10680552.

The previous prime is 21405667. The next prime is 21405673. The reversal of 21405668 is 86650412.

It is not an unprimeable number, because it can be changed into a prime (21405661) 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, 3308 + ... + 7331.

It is an arithmetic number, because the mean of its divisors is an integer number (3128160).

Almost surely, 2^21405668 is an apocalyptic number.

It is an amenable number.

21405668 is a deficient number, since it is larger than the sum of its proper divisors (16132252).

21405668 is a wasteful number, since it uses less digits than its factorization.

21405668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11146 (or 11144 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 21405668 is about 4626.6259844513. The cubic root of 21405668 is about 277.6576189754.

The spelling of 21405668 in words is "twenty-one million, four hundred five thousand, six hundred sixty-eight".