1981886261 has 4 divisors (see below), whose sum is σ = 2009800224. Its totient is φ = 1953972300.

The previous prime is 1981886243. The next prime is 1981886267. The reversal of 1981886261 is 1626881891.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981886261 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981886267) 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, 13956875 + ... + 13957016.

It is an arithmetic number, because the mean of its divisors is an integer number (502450056).

Almost surely, 2^1981886261 is an apocalyptic number.

It is an amenable number.

1981886261 is a deficient number, since it is larger than the sum of its proper divisors (27913963).

1981886261 is an equidigital number, since it uses as much as digits as its factorization.

1981886261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27913962.

The product of its digits is 331776, while the sum is 50.

The square root of 1981886261 is about 44518.3811587978. The cubic root of 1981886261 is about 1256.1058618782.

The spelling of 1981886261 in words is "one billion, nine hundred eighty-one million, eight hundred eighty-six thousand, two hundred sixty-one".