21101010251 has 2 divisors, whose sum is σ = 21101010252. Its totient is φ = 21101010250.

The previous prime is 21101010241. The next prime is 21101010341. The reversal of 21101010251 is 15201010112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21101010251 is a prime.

It is a super-2 number, since 2×21101010251² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21101010211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550505125 + 10550505126.

It is an arithmetic number, because the mean of its divisors is an integer number (10550505126).

Almost surely, 2^21101010251 is an apocalyptic number.

21101010251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101010251 is an equidigital number, since it uses as much as digits as its factorization.

21101010251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20, while the sum is 14.

Adding to 21101010251 its reverse (15201010112), we get a palindrome (36302020363).

The spelling of 21101010251 in words is "twenty-one billion, one hundred one million, ten thousand, two hundred fifty-one".