21646481 has 2 divisors, whose sum is σ = 21646482. Its totient is φ = 21646480.

The previous prime is 21646477. The next prime is 21646487. The reversal of 21646481 is 18464612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11937025 + 9709456 = 3455^2 + 3116^2 .

It is a cyclic number.

It is not a de Polignac number, because 21646481 - 2² = 21646477 is a prime.

It is a super-2 number, since 2×21646481² = 937140279366722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21646487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10823240 + 10823241.

It is an arithmetic number, because the mean of its divisors is an integer number (10823241).

Almost surely, 2^21646481 is an apocalyptic number.

It is an amenable number.

21646481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21646481 is an equidigital number, since it uses as much as digits as its factorization.

21646481 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9216, while the sum is 32.

The square root of 21646481 is about 4652.5778875802. The cubic root of 21646481 is about 278.6949514252.

The spelling of 21646481 in words is "twenty-one million, six hundred forty-six thousand, four hundred eighty-one".