661929977 has 4 divisors (see below), whose sum is σ = 665359860. Its totient is φ = 658500096.

The previous prime is 661929929. The next prime is 661929991. The reversal of 661929977 is 779929166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 779929166 = 2 ⋅389964583.

It can be written as a sum of positive squares in 2 ways, for example, as 111746041 + 550183936 = 10571^2 + 23456^2 .

It is a cyclic number.

It is not a de Polignac number, because 661929977 - 2⁸ = 661929721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661929997) 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, 1714652 + ... + 1715037.

It is an arithmetic number, because the mean of its divisors is an integer number (166339965).

Almost surely, 2^661929977 is an apocalyptic number.

It is an amenable number.

661929977 is a deficient number, since it is larger than the sum of its proper divisors (3429883).

661929977 is a wasteful number, since it uses less digits than its factorization.

661929977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3429882.

The product of its digits is 2571912, while the sum is 56.

The square root of 661929977 is about 25727.9998639614. Note that the first 3 decimals coincide. The cubic root of 661929977 is about 871.5066055599.

The spelling of 661929977 in words is "six hundred sixty-one million, nine hundred twenty-nine thousand, nine hundred seventy-seven".