82240721 has 4 divisors (see below), whose sum is σ = 86569200. Its totient is φ = 77912244.

The previous prime is 82240703. The next prime is 82240733. The reversal of 82240721 is 12704228.

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 82240721 - 2¹⁸ = 81978577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (82249721) 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, 2164211 + ... + 2164248.

It is an arithmetic number, because the mean of its divisors is an integer number (21642300).

Almost surely, 2^82240721 is an apocalyptic number.

It is an amenable number.

82240721 is a deficient number, since it is larger than the sum of its proper divisors (4328479).

82240721 is a wasteful number, since it uses less digits than its factorization.

82240721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4328478.

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 82240721 is about 9068.6669913499. Note that the first 3 decimals coincide. The cubic root of 82240721 is about 434.8728584256.

Adding to 82240721 its reverse (12704228), we get a palindrome (94944949).

The spelling of 82240721 in words is "eighty-two million, two hundred forty thousand, seven hundred twenty-one".