21657049 has 2 divisors, whose sum is σ = 21657050. Its totient is φ = 21657048.

The previous prime is 21657043. The next prime is 21657067. The reversal of 21657049 is 94075612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21529600 + 127449 = 4640^2 + 357^2 .

It is a cyclic number.

It is not a de Polignac number, because 21657049 - 2¹¹ = 21655001 is a prime.

It is not a weakly prime, because it can be changed into another prime (21657043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828524 + 10828525.

It is an arithmetic number, because the mean of its divisors is an integer number (10828525).

Almost surely, 2^21657049 is an apocalyptic number.

It is an amenable number.

21657049 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657049 is an equidigital number, since it uses as much as digits as its factorization.

21657049 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21657049 is about 4653.7134634612. The cubic root of 21657049 is about 278.7402978116.

The spelling of 21657049 in words is "twenty-one million, six hundred fifty-seven thousand, forty-nine".