638251261 has 4 divisors (see below), whose sum is σ = 639397692. Its totient is φ = 637104832.

The previous prime is 638251259. The next prime is 638251291. The reversal of 638251261 is 162152836.

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 143856036 + 494395225 = 11994^2 + 22235^2 .

It is a cyclic number.

It is not a de Polignac number, because 638251261 - 2¹ = 638251259 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 (638251291) 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, 572380 + ... + 573493.

It is an arithmetic number, because the mean of its divisors is an integer number (159849423).

Almost surely, 2^638251261 is an apocalyptic number.

It is an amenable number.

638251261 is a deficient number, since it is larger than the sum of its proper divisors (1146431).

638251261 is a wasteful number, since it uses less digits than its factorization.

638251261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1146430.

The product of its digits is 17280, while the sum is 34.

The square root of 638251261 is about 25263.6351501521. The cubic root of 638251261 is about 860.9882550401.

The spelling of 638251261 in words is "six hundred thirty-eight million, two hundred fifty-one thousand, two hundred sixty-one".