21957799 has 2 divisors, whose sum is σ = 21957800. Its totient is φ = 21957798.

The previous prime is 21957781. The next prime is 21957809. The reversal of 21957799 is 99775912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21957799 - 2⁷ = 21957671 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21957779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10978899 + 10978900.

It is an arithmetic number, because the mean of its divisors is an integer number (10978900).

Almost surely, 2^21957799 is an apocalyptic number.

21957799 is a deficient number, since it is larger than the sum of its proper divisors (1).

21957799 is an equidigital number, since it uses as much as digits as its factorization.

21957799 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 357210, while the sum is 49.

The square root of 21957799 is about 4685.9149586820. The cubic root of 21957799 is about 280.0246534415.

The spelling of 21957799 in words is "twenty-one million, nine hundred fifty-seven thousand, seven hundred ninety-nine".