21957697 has 2 divisors, whose sum is σ = 21957698. Its totient is φ = 21957696.

The previous prime is 21957671. The next prime is 21957707. The reversal of 21957697 is 79675912.

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., 17564481 + 4393216 = 4191^2 + 2096^2 .

It is a cyclic number.

It is not a de Polignac number, because 21957697 - 2⁷ = 21957569 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21957997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10978848 + 10978849.

It is an arithmetic number, because the mean of its divisors is an integer number (10978849).

Almost surely, 2^21957697 is an apocalyptic number.

It is an amenable number.

21957697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21957697 is an equidigital number, since it uses as much as digits as its factorization.

21957697 is an evil number, because the sum of its binary digits is even.

The product of its digits is 238140, while the sum is 46.

The square root of 21957697 is about 4685.9040749892. The cubic root of 21957697 is about 280.0242198437.

The spelling of 21957697 in words is "twenty-one million, nine hundred fifty-seven thousand, six hundred ninety-seven".