661808493 has 6 divisors (see below), whose sum is σ = 955945614. Its totient is φ = 441205656.

The previous prime is 661808479. The next prime is 661808519. The reversal of 661808493 is 394808166.

It can be written as a sum of positive squares in only one way, i.e., 585543204 + 76265289 = 24198^2 + 8733^2 .

It is not a de Polignac number, because 661808493 - 2⁵ = 661808461 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661808443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36767130 + ... + 36767147.

It is an arithmetic number, because the mean of its divisors is an integer number (159324269).

Almost surely, 2^661808493 is an apocalyptic number.

It is an amenable number.

661808493 is a deficient number, since it is larger than the sum of its proper divisors (294137121).

661808493 is a wasteful number, since it uses less digits than its factorization.

661808493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73534283 (or 73534280 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 45.

The square root of 661808493 is about 25725.6388258873. The cubic root of 661808493 is about 871.4532864326.

The spelling of 661808493 in words is "six hundred sixty-one million, eight hundred eight thousand, four hundred ninety-three".