581991721 has 4 divisors (see below), whose sum is σ = 582466500. Its totient is φ = 581516944.

The previous prime is 581991661. The next prime is 581991727. The reversal of 581991721 is 127199185.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 535274496 + 46717225 = 23136^2 + 6835^2 .

It is a cyclic number.

It is not a de Polignac number, because 581991721 - 2¹⁵ = 581958953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (581991727) 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, 235546 + ... + 238003.

It is an arithmetic number, because the mean of its divisors is an integer number (145616625).

Almost surely, 2^581991721 is an apocalyptic number.

It is an amenable number.

581991721 is a deficient number, since it is larger than the sum of its proper divisors (474779).

581991721 is a wasteful number, since it uses less digits than its factorization.

581991721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 474778.

The product of its digits is 45360, while the sum is 43.

The square root of 581991721 is about 24124.5045752239. The cubic root of 581991721 is about 834.9086019936.

The spelling of 581991721 in words is "five hundred eighty-one million, nine hundred ninety-one thousand, seven hundred twenty-one".