72281821 has 4 divisors (see below), whose sum is σ = 72302752. Its totient is φ = 72260892.

The previous prime is 72281791. The next prime is 72281827. The reversal of 72281821 is 12818227.

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 72281821 - 2⁹ = 72281309 is a prime.

It is a Duffinian number.

It is a zygodrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72281827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3921 + ... + 12646.

It is an arithmetic number, because the mean of its divisors is an integer number (18075688).

Almost surely, 2^72281821 is an apocalyptic number.

It is an amenable number.

72281821 is a deficient number, since it is larger than the sum of its proper divisors (20931).

72281821 is a wasteful number, since it uses less digits than its factorization.

72281821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20930.

The product of its digits is 3584, while the sum is 31.

The square root of 72281821 is about 8501.8716174734. The cubic root of 72281821 is about 416.5588461996.

The spelling of 72281821 in words is "seventy-two million, two hundred eighty-one thousand, eight hundred twenty-one".