21115222501 has 2 divisors, whose sum is σ = 21115222502. Its totient is φ = 21115222500.

The previous prime is 21115222477. The next prime is 21115222517. The reversal of 21115222501 is 10522251112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17969134401 + 3146088100 = 134049^2 + 56090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21115222501 - 2²⁷ = 20981004773 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21115222591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557611250 + 10557611251.

It is an arithmetic number, because the mean of its divisors is an integer number (10557611251).

Almost surely, 2^21115222501 is an apocalyptic number.

It is an amenable number.

21115222501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115222501 is an equidigital number, since it uses as much as digits as its factorization.

21115222501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 400, while the sum is 22.

Adding to 21115222501 its reverse (10522251112), we get a palindrome (31637473613).

The spelling of 21115222501 in words is "twenty-one billion, one hundred fifteen million, two hundred twenty-two thousand, five hundred one".