21638098957 has 2 divisors, whose sum is σ = 21638098958. Its totient is φ = 21638098956.

The previous prime is 21638098943. The next prime is 21638098961. The reversal of 21638098957 is 75989083612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20942141796 + 695957161 = 144714^2 + 26381^2 .

It is a cyclic number.

It is not a de Polignac number, because 21638098957 - 2⁷ = 21638098829 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21638098987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10819049478 + 10819049479.

It is an arithmetic number, because the mean of its divisors is an integer number (10819049479).

Almost surely, 2^21638098957 is an apocalyptic number.

It is an amenable number.

21638098957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21638098957 is an equidigital number, since it uses as much as digits as its factorization.

21638098957 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6531840, while the sum is 58.

The spelling of 21638098957 in words is "twenty-one billion, six hundred thirty-eight million, ninety-eight thousand, nine hundred fifty-seven".