21957841 has 2 divisors, whose sum is σ = 21957842. Its totient is φ = 21957840.

The previous prime is 21957811. The next prime is 21957851. The reversal of 21957841 is 14875912.

21957841 is nontrivially palindromic in base 8.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20793600 + 1164241 = 4560^2 + 1079^2 .

It is a cyclic number.

It is not a de Polignac number, because 21957841 - 2⁵ = 21957809 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21957841.

It is not a weakly prime, because it can be changed into another prime (21957811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10978920 + 10978921.

It is an arithmetic number, because the mean of its divisors is an integer number (10978921).

Almost surely, 2^21957841 is an apocalyptic number.

It is an amenable number.

21957841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21957841 is an equidigital number, since it uses as much as digits as its factorization.

21957841 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20160, while the sum is 37.

The square root of 21957841 is about 4685.9194401953. The cubic root of 21957841 is about 280.0248319814.

The spelling of 21957841 in words is "twenty-one million, nine hundred fifty-seven thousand, eight hundred forty-one".