22721813 has 4 divisors (see below), whose sum is σ = 22930380. Its totient is φ = 22513248.

The previous prime is 22721807. The next prime is 22721827. The reversal of 22721813 is 31812722.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31812722 = 2 ⋅15906361.

It can be written as a sum of positive squares in 2 ways, for example, as 8898289 + 13823524 = 2983^2 + 3718^2 .

It is a cyclic number.

It is not a de Polignac number, because 22721813 - 2²⁴ = 5944597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22721873) 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, 104120 + ... + 104337.

It is an arithmetic number, because the mean of its divisors is an integer number (5732595).

Almost surely, 2^22721813 is an apocalyptic number.

It is an amenable number.

22721813 is a deficient number, since it is larger than the sum of its proper divisors (208567).

22721813 is a wasteful number, since it uses less digits than its factorization.

22721813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208566.

The product of its digits is 1344, while the sum is 26.

The square root of 22721813 is about 4766.7402908067. The cubic root of 22721813 is about 283.2354834738.

Subtracting 22721813 from its reverse (31812722), we obtain a palindrome (9090909).

The spelling of 22721813 in words is "twenty-two million, seven hundred twenty-one thousand, eight hundred thirteen".