73720021 has 4 divisors (see below), whose sum is σ = 75712492. Its totient is φ = 71727552.

The previous prime is 73720013. The next prime is 73720027. The reversal of 73720021 is 12002737.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12002737 = 19 ⋅631723.

It can be written as a sum of positive squares in 2 ways, for example, as 66096900 + 7623121 = 8130^2 + 2761^2 .

It is a cyclic number.

It is not a de Polignac number, because 73720021 - 2³ = 73720013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 73719974 and 73720001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (73720027) 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, 996180 + ... + 996253.

It is an arithmetic number, because the mean of its divisors is an integer number (18928123).

Almost surely, 2^73720021 is an apocalyptic number.

It is an amenable number.

73720021 is a deficient number, since it is larger than the sum of its proper divisors (1992471).

73720021 is a wasteful number, since it uses less digits than its factorization.

73720021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1992470.

The product of its (nonzero) digits is 588, while the sum is 22.

The square root of 73720021 is about 8586.0363963822. The cubic root of 73720021 is about 419.3034960118.

Adding to 73720021 its reverse (12002737), we get a palindrome (85722758).

The spelling of 73720021 in words is "seventy-three million, seven hundred twenty thousand, twenty-one".