1378021644 has 72 divisors (see below), whose sum is σ = 3579287712. Its totient is φ = 446757120.

The previous prime is 1378021613. The next prime is 1378021651. The reversal of 1378021644 is 4461208731.

1378021644 is a `hidden beast` number, since 1 + 3 + 7 + 8 + 0 + 2 + 1 + 644 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 1378021599 and 1378021608.

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, 549297 + ... + 551799.

Almost surely, 2^1378021644 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 1378021644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1789643856).

1378021644 is an abundant number, since it is smaller than the sum of its proper divisors (2201266068).

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

1378021644 is a wasteful number, since it uses less digits than its factorization.

1378021644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2927 (or 2922 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The square root of 1378021644 is about 37121.7139151737. The cubic root of 1378021644 is about 1112.8040040131.

The spelling of 1378021644 in words is "one billion, three hundred seventy-eight million, twenty-one thousand, six hundred forty-four".