21009164 has 18 divisors (see below), whose sum is σ = 40166532. Its totient is φ = 9535800.

The previous prime is 21009151. The next prime is 21009167. The reversal of 21009164 is 46190012.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21009167) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 30059 + ... + 30749.

It is an arithmetic number, because the mean of its divisors is an integer number (2231474).

Almost surely, 2^21009164 is an apocalyptic number.

It is an amenable number.

21009164 is a deficient number, since it is larger than the sum of its proper divisors (19157368).

21009164 is an equidigital number, since it uses as much as digits as its factorization.

21009164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1397 (or 704 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21009164 is about 4583.5754602712. The cubic root of 21009164 is about 275.9325432007.

Adding to 21009164 its reverse (46190012), we get a palindrome (67199176).

The spelling of 21009164 in words is "twenty-one million, nine thousand, one hundred sixty-four".