75021721 has 4 divisors (see below), whose sum is σ = 75129444. Its totient is φ = 74914000.

The previous prime is 75021707. The next prime is 75021733. The reversal of 75021721 is 12712057.

It is a happy number.

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 29648025 + 45373696 = 5445^2 + 6736^2 .

It is a cyclic number.

It is not a de Polignac number, because 75021721 - 2⁷ = 75021593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (75021701) 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, 52810 + ... + 54211.

It is an arithmetic number, because the mean of its divisors is an integer number (18782361).

Almost surely, 2^75021721 is an apocalyptic number.

It is an amenable number.

75021721 is a deficient number, since it is larger than the sum of its proper divisors (107723).

75021721 is a wasteful number, since it uses less digits than its factorization.

75021721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107722.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 75021721 is about 8661.5080095789. The cubic root of 75021721 is about 421.7570402789.

Adding to 75021721 its reverse (12712057), we get a palindrome (87733778).

The spelling of 75021721 in words is "seventy-five million, twenty-one thousand, seven hundred twenty-one".