638561869 has 4 divisors (see below), whose sum is σ = 696612960. Its totient is φ = 580510780.

The previous prime is 638561867. The next prime is 638561893. The reversal of 638561869 is 968165836.

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 a cyclic number.

It is not a de Polignac number, because 638561869 - 2¹ = 638561867 is a prime.

It is a super-2 number, since 2×638561869² = 815522521081546322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638561863) 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, 29025529 + ... + 29025550.

It is an arithmetic number, because the mean of its divisors is an integer number (174153240).

Almost surely, 2^638561869 is an apocalyptic number.

It is an amenable number.

638561869 is a deficient number, since it is larger than the sum of its proper divisors (58051091).

638561869 is a wasteful number, since it uses less digits than its factorization.

638561869 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58051090.

The product of its digits is 1866240, while the sum is 52.

The square root of 638561869 is about 25269.7817362952. The cubic root of 638561869 is about 861.1279003940.

The spelling of 638561869 in words is "six hundred thirty-eight million, five hundred sixty-one thousand, eight hundred sixty-nine".