521161561 has 4 divisors (see below), whose sum is σ = 530994852. Its totient is φ = 511328272.

The previous prime is 521161559. The next prime is 521161579. The reversal of 521161561 is 165161125.

It is a happy number.

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 153289161 + 367872400 = 12381^2 + 19180^2 .

It is a cyclic number.

It is not a de Polignac number, because 521161561 - 2¹ = 521161559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (521161541) 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, 4916566 + ... + 4916671.

It is an arithmetic number, because the mean of its divisors is an integer number (132748713).

Almost surely, 2^521161561 is an apocalyptic number.

It is an amenable number.

521161561 is a deficient number, since it is larger than the sum of its proper divisors (9833291).

521161561 is an equidigital number, since it uses as much as digits as its factorization.

521161561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9833290.

The product of its digits is 1800, while the sum is 28.

The square root of 521161561 is about 22828.9632046661. The cubic root of 521161561 is about 804.7434651881.

The spelling of 521161561 in words is "five hundred twenty-one million, one hundred sixty-one thousand, five hundred sixty-one".