21304961 has 8 divisors (see below), whose sum is σ = 22599720. Its totient is φ = 20014848.

The previous prime is 21304951. The next prime is 21304963. The reversal of 21304961 is 16940312.

It can be written as a sum of positive squares in 4 ways, for example, as 4330561 + 16974400 = 2081^2 + 4120^2 .

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

It is not a de Polignac number, because 21304961 - 2⁶ = 21304897 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21304961.

It is not an unprimeable number, because it can be changed into a prime (21304963) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14195 + ... + 15623.

It is an arithmetic number, because the mean of its divisors is an integer number (2824965).

Almost surely, 2^21304961 is an apocalyptic number.

It is an amenable number.

21304961 is a deficient number, since it is larger than the sum of its proper divisors (1294759).

21304961 is a wasteful number, since it uses less digits than its factorization.

21304961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2323.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 21304961 is about 4615.7297364555. The cubic root of 21304961 is about 277.2215034608.

The spelling of 21304961 in words is "twenty-one million, three hundred four thousand, nine hundred sixty-one".