21210961 has 2 divisors, whose sum is σ = 21210962. Its totient is φ = 21210960.

The previous prime is 21210949. The next prime is 21210979. The reversal of 21210961 is 16901212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17766225 + 3444736 = 4215^2 + 1856^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210961 - 2⁵ = 21210929 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21210901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605480 + 10605481.

It is an arithmetic number, because the mean of its divisors is an integer number (10605481).

Almost surely, 2^21210961 is an apocalyptic number.

It is an amenable number.

21210961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210961 is an equidigital number, since it uses as much as digits as its factorization.

21210961 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 22.

The square root of 21210961 is about 4605.5359080133. The cubic root of 21210961 is about 276.8131910430.

The spelling of 21210961 in words is "twenty-one million, two hundred ten thousand, nine hundred sixty-one".