1638749380 has 12 divisors (see below), whose sum is σ = 3441373740. Its totient is φ = 655499744.

The previous prime is 1638749363. The next prime is 1638749407. The reversal of 1638749380 is 839478361.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 1283502276 + 355247104 = 35826^2 + 18848^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40968715 + ... + 40968754.

It is an arithmetic number, because the mean of its divisors is an integer number (286781145).

Almost surely, 2^1638749380 is an apocalyptic number.

1638749380 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1638749380 is an abundant number, since it is smaller than the sum of its proper divisors (1802624360).

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

1638749380 is a wasteful number, since it uses less digits than its factorization.

1638749380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81937478 (or 81937476 counting only the distinct ones).

The product of its (nonzero) digits is 870912, while the sum is 49.

The square root of 1638749380 is about 40481.4695879485. The cubic root of 1638749380 is about 1178.9738709350.

The spelling of 1638749380 in words is "one billion, six hundred thirty-eight million, seven hundred forty-nine thousand, three hundred eighty".