21664741 has 8 divisors (see below), whose sum is σ = 25179840. Its totient is φ = 18254688.

The previous prime is 21664739. The next prime is 21664759. The reversal of 21664741 is 14746612.

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

It is a cyclic number.

It is not a de Polignac number, because 21664741 - 2¹ = 21664739 is a prime.

It is a super-2 number, since 2×21664741² = 938722005194162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25816 + ... + 26641.

It is an arithmetic number, because the mean of its divisors is an integer number (3147480).

Almost surely, 2^21664741 is an apocalyptic number.

It is an amenable number.

21664741 is a deficient number, since it is larger than the sum of its proper divisors (3515099).

21664741 is an equidigital number, since it uses as much as digits as its factorization.

21664741 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52523.

The product of its digits is 8064, while the sum is 31.

The square root of 21664741 is about 4654.5398268787. The cubic root of 21664741 is about 278.7732942520.

The spelling of 21664741 in words is "twenty-one million, six hundred sixty-four thousand, seven hundred forty-one".