21243881 has 16 divisors (see below), whose sum is σ = 23552640. Its totient is φ = 19071360.

The previous prime is 21243857. The next prime is 21243907. The reversal of 21243881 is 18834212.

It is a cyclic number.

It is not a de Polignac number, because 21243881 - 2¹⁰ = 21242857 is a prime.

It is a super-2 number, since 2×21243881² = 902604959884322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21243821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 75461 + ... + 75741.

It is an arithmetic number, because the mean of its divisors is an integer number (1472040).

Almost surely, 2^21243881 is an apocalyptic number.

It is an amenable number.

21243881 is a deficient number, since it is larger than the sum of its proper divisors (2308759).

21243881 is a wasteful number, since it uses less digits than its factorization.

21243881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 496.

The product of its digits is 3072, while the sum is 29.

The square root of 21243881 is about 4609.1084821254. The cubic root of 21243881 is about 276.9563242707.

The spelling of 21243881 in words is "twenty-one million, two hundred forty-three thousand, eight hundred eighty-one".