21651064991 has 2 divisors, whose sum is σ = 21651064992. Its totient is φ = 21651064990.

The previous prime is 21651064961. The next prime is 21651065011. The reversal of 21651064991 is 19946015612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21651064991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21651064931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825532495 + 10825532496.

It is an arithmetic number, because the mean of its divisors is an integer number (10825532496).

Almost surely, 2^21651064991 is an apocalyptic number.

21651064991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651064991 is an equidigital number, since it uses as much as digits as its factorization.

21651064991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 116640, while the sum is 44.

The spelling of 21651064991 in words is "twenty-one billion, six hundred fifty-one million, sixty-four thousand, nine hundred ninety-one".