491521581 has 32 divisors (see below), whose sum is σ = 743930880. Its totient is φ = 320660208.

The previous prime is 491521553. The next prime is 491521603. The reversal of 491521581 is 185125194.

491521581 is a `hidden beast` number, since 49 + 15 + 21 + 581 = 666.

It is not a de Polignac number, because 491521581 - 2⁷ = 491521453 is a prime.

It is a super-2 number, since 2×491521581² = 483186929177479122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (491521531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 301290 + ... + 302916.

It is an arithmetic number, because the mean of its divisors is an integer number (23247840).

Almost surely, 2^491521581 is an apocalyptic number.

It is an amenable number.

491521581 is a deficient number, since it is larger than the sum of its proper divisors (252409299).

491521581 is a wasteful number, since it uses less digits than its factorization.

491521581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1870 (or 1864 counting only the distinct ones).

The product of its digits is 14400, while the sum is 36.

The square root of 491521581 is about 22170.2859927426. The cubic root of 491521581 is about 789.1887099396.

The spelling of 491521581 in words is "four hundred ninety-one million, five hundred twenty-one thousand, five hundred eighty-one".