661626551 has 2 divisors, whose sum is σ = 661626552. Its totient is φ = 661626550.

The previous prime is 661626547. The next prime is 661626593. The reversal of 661626551 is 155626166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661626551 - 2² = 661626547 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661623551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330813275 + 330813276.

It is an arithmetic number, because the mean of its divisors is an integer number (330813276).

Almost surely, 2^661626551 is an apocalyptic number.

661626551 is a deficient number, since it is larger than the sum of its proper divisors (1).

661626551 is an equidigital number, since it uses as much as digits as its factorization.

661626551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64800, while the sum is 38.

The square root of 661626551 is about 25722.1023829702. The cubic root of 661626551 is about 871.3734201835.

The spelling of 661626551 in words is "six hundred sixty-one million, six hundred twenty-six thousand, five hundred fifty-one".