75212721 has 6 divisors (see below), whose sum is σ = 108640610. Its totient is φ = 50141808.

The previous prime is 75212717. The next prime is 75212729. The reversal of 75212721 is 12721257.

It can be written as a sum of positive squares in only one way, i.e., 44076321 + 31136400 = 6639^2 + 5580^2 .

It is not a de Polignac number, because 75212721 - 2² = 75212717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (75212729) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4178476 + ... + 4178493.

Almost surely, 2^75212721 is an apocalyptic number.

It is an amenable number.

75212721 is a deficient number, since it is larger than the sum of its proper divisors (33427889).

75212721 is a wasteful number, since it uses less digits than its factorization.

75212721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8356975 (or 8356972 counting only the distinct ones).

The product of its digits is 1960, while the sum is 27.

The square root of 75212721 is about 8672.5267944239. The cubic root of 75212721 is about 422.1146581670.

Adding to 75212721 its reverse (12721257), we get a palindrome (87933978).

The spelling of 75212721 in words is "seventy-five million, two hundred twelve thousand, seven hundred twenty-one".