1981886861 has 4 divisors (see below), whose sum is σ = 1992263424. Its totient is φ = 1971510300.

The previous prime is 1981886857. The next prime is 1981886869. The reversal of 1981886861 is 1686881891.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1686881891 = 131 ⋅12876961.

It is a cyclic number.

It is not a de Polignac number, because 1981886861 - 2² = 1981886857 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1981886797 and 1981886806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981886869) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5187995 + ... + 5188376.

It is an arithmetic number, because the mean of its divisors is an integer number (498065856).

Almost surely, 2^1981886861 is an apocalyptic number.

It is an amenable number.

1981886861 is a deficient number, since it is larger than the sum of its proper divisors (10376563).

1981886861 is a wasteful number, since it uses less digits than its factorization.

1981886861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10376562.

The product of its digits is 1327104, while the sum is 56.

The square root of 1981886861 is about 44518.3878975868. The cubic root of 1981886861 is about 1256.1059886368.

The spelling of 1981886861 in words is "one billion, nine hundred eighty-one million, eight hundred eighty-six thousand, eight hundred sixty-one".