521665619 has 4 divisors (see below), whose sum is σ = 522783144. Its totient is φ = 520548096.

The previous prime is 521665609. The next prime is 521665633. The reversal of 521665619 is 916566125.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 521665619 - 2⁴ = 521665603 is a prime.

It is a super-2 number, since 2×521665619² = 544270036093306322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (521665609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 558062 + ... + 558995.

It is an arithmetic number, because the mean of its divisors is an integer number (130695786).

Almost surely, 2^521665619 is an apocalyptic number.

521665619 is a deficient number, since it is larger than the sum of its proper divisors (1117525).

521665619 is a wasteful number, since it uses less digits than its factorization.

521665619 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1117524.

The product of its digits is 97200, while the sum is 41.

The square root of 521665619 is about 22840.0004159369. Note that the first 3 decimals coincide. The cubic root of 521665619 is about 805.0028260127.

The spelling of 521665619 in words is "five hundred twenty-one million, six hundred sixty-five thousand, six hundred nineteen".