21810164 has 12 divisors (see below), whose sum is σ = 39827424. Its totient is φ = 10430904.

The previous prime is 21810163. The next prime is 21810169. The reversal of 21810164 is 46101812.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21810163) 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, 118442 + ... + 118625.

It is an arithmetic number, because the mean of its divisors is an integer number (3318952).

Almost surely, 2^21810164 is an apocalyptic number.

It is an amenable number.

21810164 is a deficient number, since it is larger than the sum of its proper divisors (18017260).

21810164 is a wasteful number, since it uses less digits than its factorization.

21810164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 237094 (or 237092 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 21810164 is about 4670.1353299449. The cubic root of 21810164 is about 279.3956523060.

Adding to 21810164 its reverse (46101812), we get a palindrome (67911976).

The spelling of 21810164 in words is "twenty-one million, eight hundred ten thousand, one hundred sixty-four".