661378955 has 8 divisors (see below), whose sum is σ = 819256704. Its totient is φ = 512035200.

The previous prime is 661378933. The next prime is 661378969. The reversal of 661378955 is 559873166.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661378955 - 2⁸ = 661378699 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2133326 + ... + 2133635.

It is an arithmetic number, because the mean of its divisors is an integer number (102407088).

Almost surely, 2^661378955 is an apocalyptic number.

661378955 is a deficient number, since it is larger than the sum of its proper divisors (157877749).

661378955 is a wasteful number, since it uses less digits than its factorization.

661378955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4266997.

The product of its digits is 1360800, while the sum is 50.

The square root of 661378955 is about 25717.2890289782. The cubic root of 661378955 is about 871.2647105742.

The spelling of 661378955 in words is "six hundred sixty-one million, three hundred seventy-eight thousand, nine hundred fifty-five".