55015221 has 4 divisors (see below), whose sum is σ = 73353632. Its totient is φ = 36676812.

The previous prime is 55015217. The next prime is 55015223. The reversal of 55015221 is 12251055.

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.

It is not a de Polignac number, because 55015221 - 2² = 55015217 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 (55015223) 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, 9169201 + ... + 9169206.

It is an arithmetic number, because the mean of its divisors is an integer number (18338408).

Almost surely, 2^55015221 is an apocalyptic number.

It is an amenable number.

55015221 is a deficient number, since it is larger than the sum of its proper divisors (18338411).

55015221 is a wasteful number, since it uses less digits than its factorization.

55015221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18338410.

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 55015221 is about 7417.2246157171. The cubic root of 55015221 is about 380.3303245007.

Adding to 55015221 its reverse (12251055), we get a palindrome (67266276).

The spelling of 55015221 in words is "fifty-five million, fifteen thousand, two hundred twenty-one".