21456901 has 2 divisors, whose sum is σ = 21456902. Its totient is φ = 21456900.

The previous prime is 21456893. The next prime is 21456913. The reversal of 21456901 is 10965412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16394401 + 5062500 = 4049^2 + 2250^2 .

It is a cyclic number.

It is not a de Polignac number, because 21456901 - 2³ = 21456893 is a prime.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21456901.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21456971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728450 + 10728451.

It is an arithmetic number, because the mean of its divisors is an integer number (10728451).

Almost surely, 2^21456901 is an apocalyptic number.

It is an amenable number.

21456901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21456901 is an equidigital number, since it uses as much as digits as its factorization.

21456901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21456901 is about 4632.1594316258. The cubic root of 21456901 is about 277.8789606440.

The spelling of 21456901 in words is "twenty-one million, four hundred fifty-six thousand, nine hundred one".