520001661 has 16 divisors (see below), whose sum is σ = 734595264. Its totient is φ = 326064384.

The previous prime is 520001609. The next prime is 520001681. The reversal of 520001661 is 166100025.

It is a happy number.

It is not a de Polignac number, because 520001661 - 2¹³ = 519993469 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (520001681) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 123751 + ... + 127883.

It is an arithmetic number, because the mean of its divisors is an integer number (45912204).

Almost surely, 2^520001661 is an apocalyptic number.

520001661 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

It is an amenable number.

520001661 is a deficient number, since it is larger than the sum of its proper divisors (214593603).

520001661 is a wasteful number, since it uses less digits than its factorization.

520001661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6620.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 520001661 is about 22803.5449217879. The cubic root of 520001661 is about 804.1460079253.

Adding to 520001661 its reverse (166100025), we get a palindrome (686101686).

The spelling of 520001661 in words is "five hundred twenty million, one thousand, six hundred sixty-one".