42445721 has 4 divisors (see below), whose sum is σ = 43165200. Its totient is φ = 41726244.

The previous prime is 42445709. The next prime is 42445757. The reversal of 42445721 is 12754424.

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 42445721 - 2⁶ = 42445657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (42445021) 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, 359651 + ... + 359768.

It is an arithmetic number, because the mean of its divisors is an integer number (10791300).

Almost surely, 2^42445721 is an apocalyptic number.

It is an amenable number.

42445721 is a deficient number, since it is larger than the sum of its proper divisors (719479).

42445721 is an equidigital number, since it uses as much as digits as its factorization.

42445721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 719478.

The product of its digits is 8960, while the sum is 29.

The square root of 42445721 is about 6515.0380658903. The cubic root of 42445721 is about 348.8279735555.

The spelling of 42445721 in words is "forty-two million, four hundred forty-five thousand, seven hundred twenty-one".