55229721 has 4 divisors (see below), whose sum is σ = 73639632. Its totient is φ = 36819812.

The previous prime is 55229711. The next prime is 55229761. The reversal of 55229721 is 12792255.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 55229721 - 2⁷ = 55229593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (55229701) 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, 9204951 + ... + 9204956.

It is an arithmetic number, because the mean of its divisors is an integer number (18409908).

Almost surely, 2^55229721 is an apocalyptic number.

It is an amenable number.

55229721 is a deficient number, since it is larger than the sum of its proper divisors (18409911).

55229721 is a wasteful number, since it uses less digits than its factorization.

55229721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18409910.

The product of its digits is 12600, while the sum is 33.

The square root of 55229721 is about 7431.6701353061. The cubic root of 55229721 is about 380.8239761145.

The spelling of 55229721 in words is "fifty-five million, two hundred twenty-nine thousand, seven hundred twenty-one".