521539991 has 32 divisors (see below), whose sum is σ = 650073600. Its totient is φ = 408231936.

The previous prime is 521539961. The next prime is 521540003. The reversal of 521539991 is 199935125.

It is not a de Polignac number, because 521539991 - 2¹⁰ = 521538967 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 (521539961) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1161335 + ... + 1161783.

It is an arithmetic number, because the mean of its divisors is an integer number (20314800).

Almost surely, 2^521539991 is an apocalyptic number.

521539991 is a deficient number, since it is larger than the sum of its proper divisors (128533609).

521539991 is a wasteful number, since it uses less digits than its factorization.

521539991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 743.

The product of its digits is 109350, while the sum is 44.

The square root of 521539991 is about 22837.2500752608. The cubic root of 521539991 is about 804.9382003147.

The spelling of 521539991 in words is "five hundred twenty-one million, five hundred thirty-nine thousand, nine hundred ninety-one".