21120204257 has 2 divisors, whose sum is σ = 21120204258. Its totient is φ = 21120204256.

The previous prime is 21120204239. The next prime is 21120204307. The reversal of 21120204257 is 75240202112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18238232401 + 2881971856 = 135049^2 + 53684^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120204257 - 2¹⁸ = 21119942113 is a prime.

It is not a weakly prime, because it can be changed into another prime (21120204757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560102128 + 10560102129.

It is an arithmetic number, because the mean of its divisors is an integer number (10560102129).

Almost surely, 2^21120204257 is an apocalyptic number.

It is an amenable number.

21120204257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120204257 is an equidigital number, since it uses as much as digits as its factorization.

21120204257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2240, while the sum is 26.

Adding to 21120204257 its reverse (75240202112), we get a palindrome (96360406369).

The spelling of 21120204257 in words is "twenty-one billion, one hundred twenty million, two hundred four thousand, two hundred fifty-seven".