21047657 has 2 divisors, whose sum is σ = 21047658. Its totient is φ = 21047656.

The previous prime is 21047647. The next prime is 21047669. The reversal of 21047657 is 75674012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20757136 + 290521 = 4556^2 + 539^2 .

It is a cyclic number.

It is not a de Polignac number, because 21047657 - 2⁸ = 21047401 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21047617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10523828 + 10523829.

It is an arithmetic number, because the mean of its divisors is an integer number (10523829).

Almost surely, 2^21047657 is an apocalyptic number.

It is an amenable number.

21047657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21047657 is an equidigital number, since it uses as much as digits as its factorization.

21047657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11760, while the sum is 32.

The square root of 21047657 is about 4587.7725532114. The cubic root of 21047657 is about 276.1009616282.

The spelling of 21047657 in words is "twenty-one million, forty-seven thousand, six hundred fifty-seven".