1387633644 has 72 divisors (see below), whose sum is σ = 3726755760. Its totient is φ = 434512512.

The previous prime is 1387633609. The next prime is 1387633699. The reversal of 1387633644 is 4463367831.

1387633644 is a `hidden beast` number, since 1 + 3 + 8 + 7 + 633 + 6 + 4 + 4 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 1387633644.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20667 + ... + 56589.

Almost surely, 2^1387633644 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1387633644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1863377880).

1387633644 is an abundant number, since it is smaller than the sum of its proper divisors (2339122116).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1387633644 is a wasteful number, since it uses less digits than its factorization.

1387633644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35999 (or 35994 counting only the distinct ones).

The product of its digits is 870912, while the sum is 45.

The square root of 1387633644 is about 37250.9549407797. The cubic root of 1387633644 is about 1115.3853612444.

The spelling of 1387633644 in words is "one billion, three hundred eighty-seven million, six hundred thirty-three thousand, six hundred forty-four".