661550651 has 2 divisors, whose sum is σ = 661550652. Its totient is φ = 661550650.

The previous prime is 661550641. The next prime is 661550653. The reversal of 661550651 is 156055166.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661550651 is a prime.

It is a super-3 number, since 3×661550651³ (a number of 27 digits) contains 333 as substring.

Together with 661550653, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661550653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330775325 + 330775326.

It is an arithmetic number, because the mean of its divisors is an integer number (330775326).

Almost surely, 2^661550651 is an apocalyptic number.

661550651 is a deficient number, since it is larger than the sum of its proper divisors (1).

661550651 is an equidigital number, since it uses as much as digits as its factorization.

661550651 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27000, while the sum is 35.

The square root of 661550651 is about 25720.6269558112. The cubic root of 661550651 is about 871.3400983790.

The spelling of 661550651 in words is "six hundred sixty-one million, five hundred fifty thousand, six hundred fifty-one".