21664047 has 8 divisors (see below), whose sum is σ = 30405760. Its totient is φ = 13682520.

The previous prime is 21664037. The next prime is 21664051. The reversal of 21664047 is 74046612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21664047 - 2⁷ = 21663919 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664007) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 189979 + ... + 190092.

It is an arithmetic number, because the mean of its divisors is an integer number (3800720).

Almost surely, 2^21664047 is an apocalyptic number.

21664047 is a deficient number, since it is larger than the sum of its proper divisors (8741713).

21664047 is a wasteful number, since it uses less digits than its factorization.

21664047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 380093.

The product of its (nonzero) digits is 8064, while the sum is 30.

The square root of 21664047 is about 4654.4652754103. The cubic root of 21664047 is about 278.7703175147.

The spelling of 21664047 in words is "twenty-one million, six hundred sixty-four thousand, forty-seven".