661626331651 has 2 divisors, whose sum is σ = 661626331652. Its totient is φ = 661626331650.

The previous prime is 661626331627. The next prime is 661626331661. The reversal of 661626331651 is 156133626166.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661626331651 - 2²¹ = 661624234499 is a prime.

It is not a weakly prime, because it can be changed into another prime (661626331661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330813165825 + 330813165826.

It is an arithmetic number, because the mean of its divisors is an integer number (330813165826).

Almost surely, 2^661626331651 is an apocalyptic number.

661626331651 is a deficient number, since it is larger than the sum of its proper divisors (1).

661626331651 is an equidigital number, since it uses as much as digits as its factorization.

661626331651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 699840, while the sum is 46.

The spelling of 661626331651 in words is "six hundred sixty-one billion, six hundred twenty-six million, three hundred thirty-one thousand, six hundred fifty-one".