661378897 has 8 divisors (see below), whose sum is σ = 711764712. Its totient is φ = 612268800.

The previous prime is 661378889. The next prime is 661378933. The reversal of 661378897 is 798873166.

It can be written as a sum of positive squares in 4 ways, for example, as 148084561 + 513294336 = 12169^2 + 22656^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 661378897 - 2³ = 661378889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661378807) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 317854 + ... + 319927.

It is an arithmetic number, because the mean of its divisors is an integer number (88970589).

Almost surely, 2^661378897 is an apocalyptic number.

It is an amenable number.

661378897 is a deficient number, since it is larger than the sum of its proper divisors (50385815).

661378897 is a wasteful number, since it uses less digits than its factorization.

661378897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 637859.

The product of its digits is 3048192, while the sum is 55.

The square root of 661378897 is about 25717.2879013321. The cubic root of 661378897 is about 871.2646851055.

The spelling of 661378897 in words is "six hundred sixty-one million, three hundred seventy-eight thousand, eight hundred ninety-seven".