5581991981 has 4 divisors (see below), whose sum is σ = 5711805792. Its totient is φ = 5452178172.

The previous prime is 5581991977. The next prime is 5581991983. The reversal of 5581991981 is 1891991855.

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 not a de Polignac number, because 5581991981 - 2² = 5581991977 is a prime.

It is a super-2 number, since 2×5581991981² = 62317268951896608722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (5581991983) 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, 64906841 + ... + 64906926.

It is an arithmetic number, because the mean of its divisors is an integer number (1427951448).

Almost surely, 2^5581991981 is an apocalyptic number.

It is an amenable number.

5581991981 is a deficient number, since it is larger than the sum of its proper divisors (129813811).

5581991981 is a wasteful number, since it uses less digits than its factorization.

5581991981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129813810.

The product of its digits is 1166400, while the sum is 56.

The square root of 5581991981 is about 74712.7297118771. The cubic root of 5581991981 is about 1773.9024603968.

The spelling of 5581991981 in words is "five billion, five hundred eighty-one million, nine hundred ninety-one thousand, nine hundred eighty-one".