64173721 has 4 divisors (see below), whose sum is σ = 64440244. Its totient is φ = 63907200.

The previous prime is 64173713. The next prime is 64173743. The reversal of 64173721 is 12737146.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 59598400 + 4575321 = 7720^2 + 2139^2 .

It is a cyclic number.

It is not a de Polignac number, because 64173721 - 2³ = 64173713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (64173121) 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, 132900 + ... + 133381.

It is an arithmetic number, because the mean of its divisors is an integer number (16110061).

Almost surely, 2^64173721 is an apocalyptic number.

It is an amenable number.

64173721 is a deficient number, since it is larger than the sum of its proper divisors (266523).

64173721 is a wasteful number, since it uses less digits than its factorization.

64173721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266522.

The product of its digits is 7056, while the sum is 31.

The square root of 64173721 is about 8010.8502045663. The cubic root of 64173721 is about 400.3615917800.

The spelling of 64173721 in words is "sixty-four million, one hundred seventy-three thousand, seven hundred twenty-one".