638560261 has 8 divisors (see below), whose sum is σ = 650125304. Its totient is φ = 627030720.

The previous prime is 638560231. The next prime is 638560267. The reversal of 638560261 is 162065836.

It can be written as a sum of positive squares in 4 ways, for example, as 58232161 + 580328100 = 7631^2 + 24090^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638560261 - 2⁵ = 638560229 is a prime.

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 638560261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638560267) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28855 + ... + 45931.

It is an arithmetic number, because the mean of its divisors is an integer number (81265663).

Almost surely, 2^638560261 is an apocalyptic number.

638560261 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

638560261 is a deficient number, since it is larger than the sum of its proper divisors (11565043).

638560261 is a wasteful number, since it uses less digits than its factorization.

638560261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17751.

The product of its (nonzero) digits is 51840, while the sum is 37.

The square root of 638560261 is about 25269.7499196173. The cubic root of 638560261 is about 861.1271775745.

The spelling of 638560261 in words is "six hundred thirty-eight million, five hundred sixty thousand, two hundred sixty-one".