661777799 has 4 divisors (see below), whose sum is σ = 661910760. Its totient is φ = 661644840.

The previous prime is 661777793. The next prime is 661777829. The reversal of 661777799 is 997777166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 997777166 = 2 ⋅498888583.

It is a cyclic number.

It is not a de Polignac number, because 661777799 - 2¹² = 661773703 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661777793) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 58712 + ... + 69069.

It is an arithmetic number, because the mean of its divisors is an integer number (165477690).

Almost surely, 2^661777799 is an apocalyptic number.

661777799 is a deficient number, since it is larger than the sum of its proper divisors (132961).

661777799 is a wasteful number, since it uses less digits than its factorization.

661777799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132960.

The product of its digits is 7001316, while the sum is 59.

The square root of 661777799 is about 25725.0422545814. The cubic root of 661777799 is about 871.4398138540.

The spelling of 661777799 in words is "six hundred sixty-one million, seven hundred seventy-seven thousand, seven hundred ninety-nine".