21164961 has 4 divisors (see below), whose sum is σ = 28219952. Its totient is φ = 14109972.

The previous prime is 21164953. The next prime is 21164989. The reversal of 21164961 is 16946112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21164961 - 2³ = 21164953 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21166961) 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, 3527491 + ... + 3527496.

It is an arithmetic number, because the mean of its divisors is an integer number (7054988).

Almost surely, 2^21164961 is an apocalyptic number.

It is an amenable number.

21164961 is a deficient number, since it is larger than the sum of its proper divisors (7054991).

21164961 is an equidigital number, since it uses as much as digits as its factorization.

21164961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7054990.

The product of its digits is 2592, while the sum is 30.

The square root of 21164961 is about 4600.5392075277. The cubic root of 21164961 is about 276.6129388742.

The spelling of 21164961 in words is "twenty-one million, one hundred sixty-four thousand, nine hundred sixty-one".