1581407991 has 12 divisors (see below), whose sum is σ = 2357942080. Its totient is φ = 1020263040.

The previous prime is 1581407977. The next prime is 1581407999. The reversal of 1581407991 is 1997041851.

It is a happy number.

1581407991 is a `hidden beast` number, since 158 + 1 + 407 + 9 + 91 = 666.

It is not a de Polignac number, because 1581407991 - 2⁵ = 1581407959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1581407999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2833786 + ... + 2834343.

Almost surely, 2^1581407991 is an apocalyptic number.

1581407991 is a deficient number, since it is larger than the sum of its proper divisors (776534089).

1581407991 is a wasteful number, since it uses less digits than its factorization.

1581407991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5668166 (or 5668163 counting only the distinct ones).

The product of its (nonzero) digits is 90720, while the sum is 45.

The square root of 1581407991 is about 39766.9208136612. The cubic root of 1581407991 is about 1165.0591534861.

The spelling of 1581407991 in words is "one billion, five hundred eighty-one million, four hundred seven thousand, nine hundred ninety-one".