75721561 has 4 divisors (see below), whose sum is σ = 78164224. Its totient is φ = 73278900.

The previous prime is 75721549. The next prime is 75721627. The reversal of 75721561 is 16512757.

It is a happy number.

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 75721561 - 2⁷ = 75721433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (75721511) 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 in 3 ways as a sum of consecutive naturals, for example, 1221285 + ... + 1221346.

It is an arithmetic number, because the mean of its divisors is an integer number (19541056).

Almost surely, 2^75721561 is an apocalyptic number.

It is an amenable number.

75721561 is a deficient number, since it is larger than the sum of its proper divisors (2442663).

75721561 is a wasteful number, since it uses less digits than its factorization.

75721561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2442662.

The product of its digits is 14700, while the sum is 34.

The square root of 75721561 is about 8701.8136615306. The cubic root of 75721561 is about 423.0644366029.

The spelling of 75721561 in words is "seventy-five million, seven hundred twenty-one thousand, five hundred sixty-one".