21668673 has 24 divisors (see below), whose sum is σ = 31739520. Its totient is φ = 13141440.

The previous prime is 21668629. The next prime is 21668681. The reversal of 21668673 is 37686612.

It is not a de Polignac number, because 21668673 - 2⁶ = 21668609 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (21669673) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39783 + ... + 40323.

It is an arithmetic number, because the mean of its divisors is an integer number (1322480).

Almost surely, 2^21668673 is an apocalyptic number.

It is an amenable number.

21668673 is a deficient number, since it is larger than the sum of its proper divisors (10070847).

21668673 is a wasteful number, since it uses less digits than its factorization.

21668673 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 649 (or 636 counting only the distinct ones).

The product of its digits is 72576, while the sum is 39.

The square root of 21668673 is about 4654.9621910387. The cubic root of 21668673 is about 278.7901583707.

The spelling of 21668673 in words is "twenty-one million, six hundred sixty-eight thousand, six hundred seventy-three".