21646057 has 2 divisors, whose sum is σ = 21646058. Its totient is φ = 21646056.

The previous prime is 21646043. The next prime is 21646067. The reversal of 21646057 is 75064612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16128256 + 5517801 = 4016^2 + 2349^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21646057 is a prime.

It is not a weakly prime, because it can be changed into another prime (21646067) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10823028 + 10823029.

It is an arithmetic number, because the mean of its divisors is an integer number (10823029).

Almost surely, 2^21646057 is an apocalyptic number.

It is an amenable number.

21646057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21646057 is an equidigital number, since it uses as much as digits as its factorization.

21646057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 21646057 is about 4652.5323212203. The cubic root of 21646057 is about 278.6931317694.

It can be divided in two parts, 2164605 and 7, that added together give a palindrome (2164612).

The spelling of 21646057 in words is "twenty-one million, six hundred forty-six thousand, fifty-seven".