21705164 has 48 divisors (see below), whose sum is σ = 42674688. Its totient is φ = 9595968.

The previous prime is 21705161. The next prime is 21705191. The reversal of 21705164 is 46150712.

It is a super-2 number, since 2×21705164² = 942228288533792, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is not an unprimeable number, because it can be changed into a prime (21705161) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 202799 + ... + 202905.

It is an arithmetic number, because the mean of its divisors is an integer number (889056).

Almost surely, 2^21705164 is an apocalyptic number.

It is an amenable number.

21705164 is a deficient number, since it is larger than the sum of its proper divisors (20969524).

21705164 is a wasteful number, since it uses less digits than its factorization.

21705164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 254 (or 252 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 21705164 is about 4658.8801229480. The cubic root of 21705164 is about 278.9465689059.

Adding to 21705164 its reverse (46150712), we get a palindrome (67855876).

The spelling of 21705164 in words is "twenty-one million, seven hundred five thousand, one hundred sixty-four".