521688991 has 2 divisors, whose sum is σ = 521688992. Its totient is φ = 521688990.

The previous prime is 521688983. The next prime is 521688997. The reversal of 521688991 is 199886125.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 521688991 - 2³ = 521688983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (521688997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260844495 + 260844496.

It is an arithmetic number, because the mean of its divisors is an integer number (260844496).

Almost surely, 2^521688991 is an apocalyptic number.

521688991 is a deficient number, since it is larger than the sum of its proper divisors (1).

521688991 is an equidigital number, since it uses as much as digits as its factorization.

521688991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 49.

The square root of 521688991 is about 22840.5120564317. The cubic root of 521688991 is about 805.0148479187.

The spelling of 521688991 in words is "five hundred twenty-one million, six hundred eighty-eight thousand, nine hundred ninety-one".