1981555290 has 144 divisors (see below), whose sum is σ = 6099040584. Its totient is φ = 443393280.

The previous prime is 1981555243. The next prime is 1981555307. The reversal of 1981555290 is 925551891.

1981555290 is a `hidden beast` number, since 1 + 9 + 8 + 1 + 5 + 552 + 90 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 1225910169 + 755645121 = 35013^2 + 27489^2 .

It is a super-2 number, since 2×1981555290² = 7853122734653968200, which contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 134572 + ... + 148568.

Almost surely, 2^1981555290 is an apocalyptic number.

1981555290 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1981555290, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3049520292).

1981555290 is an abundant number, since it is smaller than the sum of its proper divisors (4117485294).

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

1981555290 is a wasteful number, since it uses less digits than its factorization.

1981555290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14045 (or 14031 counting only the distinct ones).

The product of its (nonzero) digits is 162000, while the sum is 45.

The square root of 1981555290 is about 44514.6637637532. The cubic root of 1981555290 is about 1256.0359356055.

The spelling of 1981555290 in words is "one billion, nine hundred eighty-one million, five hundred fifty-five thousand, two hundred ninety".