505220021 has 4 divisors (see below), whose sum is σ = 507865344. Its totient is φ = 502574700.

The previous prime is 505220017. The next prime is 505220041. The reversal of 505220021 is 120022505.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 120022505 = 5 ⋅24004501.

It is a cyclic number.

It is not a de Polignac number, because 505220021 - 2² = 505220017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (505220011) 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, 1322375 + ... + 1322756.

It is an arithmetic number, because the mean of its divisors is an integer number (126966336).

Almost surely, 2^505220021 is an apocalyptic number.

It is an amenable number.

505220021 is a deficient number, since it is larger than the sum of its proper divisors (2645323).

505220021 is a wasteful number, since it uses less digits than its factorization.

505220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2645322.

The product of its (nonzero) digits is 200, while the sum is 17.

The square root of 505220021 is about 22477.0999241450. The cubic root of 505220021 is about 796.4530581835.

Adding to 505220021 its reverse (120022505), we get a palindrome (625242526).

The spelling of 505220021 in words is "five hundred five million, two hundred twenty thousand, twenty-one".