21867813 has 40 divisors (see below), whose sum is σ = 36137376. Its totient is φ = 13122000.

The previous prime is 21867773. The next prime is 21867821. The reversal of 21867813 is 31876812.

It is a de Polignac number, because none of the positive numbers 2^k-21867813 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21867823) 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 39 ways as a sum of consecutive naturals, for example, 216463 + ... + 216563.

It is a vampire number, since it can be written as 2673 ⋅ 8181 (with its own digits).

Almost surely, 2^21867813 is an apocalyptic number.

It is an amenable number.

21867813 is a deficient number, since it is larger than the sum of its proper divisors (14269563).

21867813 is an frugal number, since it uses more digits than its factorization.

21867813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139 (or 115 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 21867813 is about 4676.3033477310. The cubic root of 21867813 is about 279.6416035276.

It can be divided in two parts, 2186 and 7813, that added together give a palindrome (9999).

The spelling of 21867813 in words is "twenty-one million, eight hundred sixty-seven thousand, eight hundred thirteen".