21101212021957 has 2 divisors, whose sum is σ = 21101212021958. Its totient is φ = 21101212021956.

The previous prime is 21101212021937. The next prime is 21101212022029. The reversal of 21101212021957 is 75912021210112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11807408588481 + 9293803433476 = 3436191^2 + 3048574^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101212021957 - 2¹⁵ = 21101211989189 is a prime.

It is a super-2 number, since 2×21101212021957² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101212021927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550606010978 + 10550606010979.

It is an arithmetic number, because the mean of its divisors is an integer number (10550606010979).

Almost surely, 2^{21101212021957} is an apocalyptic number.

It is an amenable number.

21101212021957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101212021957 is an equidigital number, since it uses as much as digits as its factorization.

21101212021957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5040, while the sum is 34.

The spelling of 21101212021957 in words is "twenty-one trillion, one hundred one billion, two hundred twelve million, twenty-one thousand, nine hundred fifty-seven".