21002000251 has 2 divisors, whose sum is σ = 21002000252. Its totient is φ = 21002000250.

The previous prime is 21002000233. The next prime is 21002000293. The reversal of 21002000251 is 15200020012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21002000251 - 2²³ = 20993611643 is a prime.

It is not a weakly prime, because it can be changed into another prime (21002000221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501000125 + 10501000126.

It is an arithmetic number, because the mean of its divisors is an integer number (10501000126).

Almost surely, 2^21002000251 is an apocalyptic number.

21002000251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002000251 is an equidigital number, since it uses as much as digits as its factorization.

21002000251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40, while the sum is 13.

Adding to 21002000251 its reverse (15200020012), we get a palindrome (36202020263).

The spelling of 21002000251 in words is "twenty-one billion, two million, two hundred fifty-one", and thus it is an aban number.