521666557 has 2 divisors, whose sum is σ = 521666558. Its totient is φ = 521666556.

The previous prime is 521666533. The next prime is 521666581. The reversal of 521666557 is 755666125.

It is a balanced prime because it is at equal distance from previous prime (521666533) and next prime (521666581).

It can be written as a sum of positive squares in only one way, i.e., 288524196 + 233142361 = 16986^2 + 15269^2 .

It is a cyclic number.

It is not a de Polignac number, because 521666557 - 2¹⁵ = 521633789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (521666507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260833278 + 260833279.

It is an arithmetic number, because the mean of its divisors is an integer number (260833279).

Almost surely, 2^521666557 is an apocalyptic number.

It is an amenable number.

521666557 is a deficient number, since it is larger than the sum of its proper divisors (1).

521666557 is an equidigital number, since it uses as much as digits as its factorization.

521666557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 378000, while the sum is 43.

The square root of 521666557 is about 22840.0209500780. The cubic root of 521666557 is about 805.0033085007.

The spelling of 521666557 in words is "five hundred twenty-one million, six hundred sixty-six thousand, five hundred fifty-seven".