55721405 has 4 divisors (see below), whose sum is σ = 66865692. Its totient is φ = 44577120.

The previous prime is 55721401. The next prime is 55721417. The reversal of 55721405 is 50412755.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50412755 = 5 ⋅10082551.

It can be written as a sum of positive squares in 2 ways, for example, as 36264484 + 19456921 = 6022^2 + 4411^2 .

It is not a de Polignac number, because 55721405 - 2² = 55721401 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55721401) 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, 5572136 + ... + 5572145.

It is an arithmetic number, because the mean of its divisors is an integer number (16716423).

Almost surely, 2^55721405 is an apocalyptic number.

It is an amenable number.

55721405 is a deficient number, since it is larger than the sum of its proper divisors (11144287).

55721405 is a wasteful number, since it uses less digits than its factorization.

55721405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11144286.

The product of its (nonzero) digits is 7000, while the sum is 29.

The square root of 55721405 is about 7464.6771530991. The cubic root of 55721405 is about 381.9507374135.

The spelling of 55721405 in words is "fifty-five million, seven hundred twenty-one thousand, four hundred five".