661679881 has 2 divisors, whose sum is σ = 661679882. Its totient is φ = 661679880.

The previous prime is 661679869. The next prime is 661679891. The reversal of 661679881 is 188976166.

It is a happy number.

661679881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 445589881 + 216090000 = 21109^2 + 14700^2 .

It is a cyclic number.

It is not a de Polignac number, because 661679881 - 2²⁹ = 124808969 is a prime.

It is a super-2 number, since 2×661679881² = 875640529840348322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (661679861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330839940 + 330839941.

It is an arithmetic number, because the mean of its divisors is an integer number (330839941).

Almost surely, 2^661679881 is an apocalyptic number.

It is an amenable number.

661679881 is a deficient number, since it is larger than the sum of its proper divisors (1).

661679881 is an equidigital number, since it uses as much as digits as its factorization.

661679881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 870912, while the sum is 52.

The square root of 661679881 is about 25723.1390191788. The cubic root of 661679881 is about 871.3968317268.

The spelling of 661679881 in words is "six hundred sixty-one million, six hundred seventy-nine thousand, eight hundred eighty-one".