661953779 has 2 divisors, whose sum is σ = 661953780. Its totient is φ = 661953778.

The previous prime is 661953767. The next prime is 661953811. The reversal of 661953779 is 977359166.

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-661953779 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 661953779.

It is not a weakly prime, because it can be changed into another prime (661953709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330976889 + 330976890.

It is an arithmetic number, because the mean of its divisors is an integer number (330976890).

Almost surely, 2^661953779 is an apocalyptic number.

661953779 is a deficient number, since it is larger than the sum of its proper divisors (1).

661953779 is an equidigital number, since it uses as much as digits as its factorization.

661953779 is an evil number, because the sum of its binary digits is even.

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

The square root of 661953779 is about 25728.4624297683. The cubic root of 661953779 is about 871.5170514541.

The spelling of 661953779 in words is "six hundred sixty-one million, nine hundred fifty-three thousand, seven hundred seventy-nine".