21700957 has 2 divisors, whose sum is σ = 21700958. Its totient is φ = 21700956.

The previous prime is 21700949. The next prime is 21700963. The reversal of 21700957 is 75900712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15912121 + 5788836 = 3989^2 + 2406^2 .

It is a cyclic number.

It is not a de Polignac number, because 21700957 - 2³ = 21700949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21700057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850478 + 10850479.

It is an arithmetic number, because the mean of its divisors is an integer number (10850479).

Almost surely, 2^21700957 is an apocalyptic number.

It is an amenable number.

21700957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21700957 is an equidigital number, since it uses as much as digits as its factorization.

21700957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4410, while the sum is 31.

The square root of 21700957 is about 4658.4285977140. The cubic root of 21700957 is about 278.9285454831.

The spelling of 21700957 in words is "twenty-one million, seven hundred thousand, nine hundred fifty-seven".