661893807 has 4 divisors (see below), whose sum is σ = 882525080. Its totient is φ = 441262536.

The previous prime is 661893779. The next prime is 661893821. The reversal of 661893807 is 708398166.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 661893807 - 2¹⁰ = 661892783 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661893857) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 110315632 + ... + 110315637.

It is an arithmetic number, because the mean of its divisors is an integer number (220631270).

Almost surely, 2^661893807 is an apocalyptic number.

661893807 is a deficient number, since it is larger than the sum of its proper divisors (220631273).

661893807 is a wasteful number, since it uses less digits than its factorization.

661893807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220631272.

The product of its (nonzero) digits is 435456, while the sum is 48.

The square root of 661893807 is about 25727.2969236957. The cubic root of 661893807 is about 871.4907312886.

It can be divided in two parts, 66189 and 3807, that added together give a palindrome (69996).

The spelling of 661893807 in words is "six hundred sixty-one million, eight hundred ninety-three thousand, eight hundred seven".