55491721 has 4 divisors (see below), whose sum is σ = 55636992. Its totient is φ = 55346452.

The previous prime is 55491691. The next prime is 55491769. The reversal of 55491721 is 12719455.

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 55491721 - 2¹⁷ = 55360649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (55491781) 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, 72061 + ... + 72826.

It is an arithmetic number, because the mean of its divisors is an integer number (13909248).

Almost surely, 2^55491721 is an apocalyptic number.

It is an amenable number.

55491721 is a deficient number, since it is larger than the sum of its proper divisors (145271).

55491721 is a wasteful number, since it uses less digits than its factorization.

55491721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145270.

The product of its digits is 12600, while the sum is 34.

The square root of 55491721 is about 7449.2765420543. The cubic root of 55491721 is about 381.4252135244.

The spelling of 55491721 in words is "fifty-five million, four hundred ninety-one thousand, seven hundred twenty-one".