661938769 has 4 divisors (see below), whose sum is σ = 679829044. Its totient is φ = 644048496.

The previous prime is 661938757. The next prime is 661938773. The reversal of 661938769 is 967839166.

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

It can be written as a sum of positive squares in 2 ways, for example, as 381811600 + 280127169 = 19540^2 + 16737^2 .

It is a cyclic number.

It is not a de Polignac number, because 661938769 - 2⁵ = 661938737 is a prime.

It is a super-2 number, since 2×661938769² = 876325867810470722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661938869) 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, 8945082 + ... + 8945155.

It is an arithmetic number, because the mean of its divisors is an integer number (169957261).

Almost surely, 2^661938769 is an apocalyptic number.

It is an amenable number.

661938769 is a deficient number, since it is larger than the sum of its proper divisors (17890275).

661938769 is a wasteful number, since it uses less digits than its factorization.

661938769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17890274.

The product of its digits is 2939328, while the sum is 55.

The square root of 661938769 is about 25728.1707278228. The cubic root of 661938769 is about 871.5104641010.

The spelling of 661938769 in words is "six hundred sixty-one million, nine hundred thirty-eight thousand, seven hundred sixty-nine".