21201021748957 has 2 divisors, whose sum is σ = 21201021748958. Its totient is φ = 21201021748956.

The previous prime is 21201021748937. The next prime is 21201021749057. The reversal of 21201021748957 is 75984712010212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21197746018201 + 3275730756 = 4604101^2 + 57234^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201021748957 - 2¹¹ = 21201021746909 is a prime.

It is a super-2 number, since 2×21201021748957² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21201021748957.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201021748927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600510874478 + 10600510874479.

It is an arithmetic number, because the mean of its divisors is an integer number (10600510874479).

Almost surely, 2^{21201021748957} is an apocalyptic number.

It is an amenable number.

21201021748957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201021748957 is an equidigital number, since it uses as much as digits as its factorization.

21201021748957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 564480, while the sum is 49.

The spelling of 21201021748957 in words is "twenty-one trillion, two hundred one billion, twenty-one million, seven hundred forty-eight thousand, nine hundred fifty-seven".