75721021 has 2 divisors, whose sum is σ = 75721022. Its totient is φ = 75721020.

The previous prime is 75720989. The next prime is 75721027. The reversal of 75721021 is 12012757.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61387225 + 14333796 = 7835^2 + 3786^2 .

It is a cyclic number.

It is not a de Polignac number, because 75721021 - 2⁵ = 75720989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (75721027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 37860510 + 37860511.

It is an arithmetic number, because the mean of its divisors is an integer number (37860511).

Almost surely, 2^75721021 is an apocalyptic number.

It is an amenable number.

75721021 is a deficient number, since it is larger than the sum of its proper divisors (1).

75721021 is an equidigital number, since it uses as much as digits as its factorization.

75721021 is an odious number, because the sum of its binary digits is odd.

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

The square root of 75721021 is about 8701.7826334608. The cubic root of 75721021 is about 423.0634309213.

Adding to 75721021 its reverse (12012757), we get a palindrome (87733778).

The spelling of 75721021 in words is "seventy-five million, seven hundred twenty-one thousand, twenty-one".