21002220121957 has 2 divisors, whose sum is σ = 21002220121958. Its totient is φ = 21002220121956.

The previous prime is 21002220121943. The next prime is 21002220122041. The reversal of 21002220121957 is 75912102220012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20628319669281 + 373900452676 = 4541841^2 + 611474^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002220121957 is a prime.

It is a super-2 number, since 2×21002220121957² (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 (21002220122957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501110060978 + 10501110060979.

It is an arithmetic number, because the mean of its divisors is an integer number (10501110060979).

Almost surely, 2^{21002220121957} is an apocalyptic number.

It is an amenable number.

21002220121957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002220121957 is an equidigital number, since it uses as much as digits as its factorization.

21002220121957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 34.

Adding to 21002220121957 its reverse (75912102220012), we get a palindrome (96914322341969).

The spelling of 21002220121957 in words is "twenty-one trillion, two billion, two hundred twenty million, one hundred twenty-one thousand, nine hundred fifty-seven".