521111681 has 8 divisors (see below), whose sum is σ = 534209928. Its totient is φ = 508334400.

The previous prime is 521111641. The next prime is 521111719. The reversal of 521111681 is 186111125.

It can be written as a sum of positive squares in 4 ways, for example, as 361342081 + 159769600 = 19009^2 + 12640^2 .

It is not a de Polignac number, because 521111681 - 2²² = 516917377 is a prime.

It is a super-2 number, since 2×521111681² = 543114768149291522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 521111681.

It is not an unprimeable number, because it can be changed into a prime (521111641) 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 7 ways as a sum of consecutive naturals, for example, 65141 + ... + 72701.

It is an arithmetic number, because the mean of its divisors is an integer number (66776241).

Almost surely, 2^521111681 is an apocalyptic number.

It is an amenable number.

521111681 is a deficient number, since it is larger than the sum of its proper divisors (13098247).

521111681 is an frugal number, since it uses more digits than its factorization.

521111681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7684 (or 7602 counting only the distinct ones).

The product of its digits is 480, while the sum is 26.

The square root of 521111681 is about 22827.8707066603. The cubic root of 521111681 is about 804.7177905619.

The spelling of 521111681 in words is "five hundred twenty-one million, one hundred eleven thousand, six hundred eighty-one".