1981377818 has 12 divisors (see below), whose sum is σ = 3457302282. Its totient is φ = 849161880.

The previous prime is 1981377809. The next prime is 1981377833. The reversal of 1981377818 is 8187731891.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 1901221609 + 80156209 = 43603^2 + 8953^2 .

It is a super-3 number, since 3×1981377818³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 1981377818.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10108973 + ... + 10109168.

Almost surely, 2^1981377818 is an apocalyptic number.

1981377818 is a deficient number, since it is larger than the sum of its proper divisors (1475924464).

1981377818 is a wasteful number, since it uses less digits than its factorization.

1981377818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20218157 (or 20218150 counting only the distinct ones).

The product of its digits is 677376, while the sum is 53.

The square root of 1981377818 is about 44512.6703085762. The cubic root of 1981377818 is about 1255.9984368008.

The spelling of 1981377818 in words is "one billion, nine hundred eighty-one million, three hundred seventy-seven thousand, eight hundred eighteen".