1638172909720 has 32 divisors (see below), whose sum is σ = 3764312222400. Its totient is φ = 641327266048.

The previous prime is 1638172909699. The next prime is 1638172909721. The reversal of 1638172909720 is 279092718361.

It is a happy number.

It is a super-2 number, since 2×1638172909720² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638172909721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 435682405 + ... + 435686164.

It is an arithmetic number, because the mean of its divisors is an integer number (117634756950).

Almost surely, 2^{1638172909720} is an apocalyptic number.

1638172909720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1638172909720 is an abundant number, since it is smaller than the sum of its proper divisors (2126139312680).

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

1638172909720 is a wasteful number, since it uses less digits than its factorization.

1638172909720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 871368627 (or 871368623 counting only the distinct ones).

The product of its (nonzero) digits is 2286144, while the sum is 55.

The spelling of 1638172909720 in words is "one trillion, six hundred thirty-eight billion, one hundred seventy-two million, nine hundred nine thousand, seven hundred twenty".