661317889 has 2 divisors, whose sum is σ = 661317890. Its totient is φ = 661317888.

The previous prime is 661317883. The next prime is 661317907. The reversal of 661317889 is 988713166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 487526400 + 173791489 = 22080^2 + 13183^2 .

It is a cyclic number.

It is not a de Polignac number, because 661317889 - 2¹³ = 661309697 is a prime.

It is a super-2 number, since 2×661317889² = 874682700622832642, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (661317883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330658944 + 330658945.

It is an arithmetic number, because the mean of its divisors is an integer number (330658945).

Almost surely, 2^661317889 is an apocalyptic number.

It is an amenable number.

661317889 is a deficient number, since it is larger than the sum of its proper divisors (1).

661317889 is an equidigital number, since it uses as much as digits as its factorization.

661317889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 435456, while the sum is 49.

The square root of 661317889 is about 25716.1017457934. The cubic root of 661317889 is about 871.2378947384.

The spelling of 661317889 in words is "six hundred sixty-one million, three hundred seventeen thousand, eight hundred eighty-nine".