661539779 has 2 divisors, whose sum is σ = 661539780. Its totient is φ = 661539778.

The previous prime is 661539773. The next prime is 661539833. The reversal of 661539779 is 977935166.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661539779 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 661539779.

It is not a weakly prime, because it can be changed into another prime (661539773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330769889 + 330769890.

It is an arithmetic number, because the mean of its divisors is an integer number (330769890).

Almost surely, 2^661539779 is an apocalyptic number.

661539779 is a deficient number, since it is larger than the sum of its proper divisors (1).

661539779 is an equidigital number, since it uses as much as digits as its factorization.

661539779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2143260, while the sum is 53.

The square root of 661539779 is about 25720.4156070620. The cubic root of 661539779 is about 871.3353251182.

The spelling of 661539779 in words is "six hundred sixty-one million, five hundred thirty-nine thousand, seven hundred seventy-nine".