665069781 has 4 divisors (see below), whose sum is σ = 886759712. Its totient is φ = 443379852.

The previous prime is 665069773. The next prime is 665069791. The reversal of 665069781 is 187960566.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 665069781 - 2³ = 665069773 is a prime.

It is a super-2 number, since 2×665069781² = 884635627198775922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 665069781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665069761) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110844961 + ... + 110844966.

It is an arithmetic number, because the mean of its divisors is an integer number (221689928).

Almost surely, 2^665069781 is an apocalyptic number.

It is an amenable number.

665069781 is a deficient number, since it is larger than the sum of its proper divisors (221689931).

665069781 is a wasteful number, since it uses less digits than its factorization.

665069781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221689930.

The product of its (nonzero) digits is 544320, while the sum is 48.

The square root of 665069781 is about 25788.9468765206. The cubic root of 665069781 is about 872.8824030155.

The spelling of 665069781 in words is "six hundred sixty-five million, sixty-nine thousand, seven hundred eighty-one".