21368881 has 4 divisors (see below), whose sum is σ = 22625892. Its totient is φ = 20111872.

The previous prime is 21368861. The next prime is 21368899. The reversal of 21368881 is 18886312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18533025 + 2835856 = 4305^2 + 1684^2 .

It is a cyclic number.

It is not a de Polignac number, because 21368881 - 2¹¹ = 21366833 is a prime.

It is a super-2 number, since 2×21368881² = 913258150384322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21368881.

It is not an unprimeable number, because it can be changed into a prime (21368801) 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, 628480 + ... + 628513.

It is an arithmetic number, because the mean of its divisors is an integer number (5656473).

Almost surely, 2^21368881 is an apocalyptic number.

It is an amenable number.

21368881 is a deficient number, since it is larger than the sum of its proper divisors (1257011).

21368881 is a wasteful number, since it uses less digits than its factorization.

21368881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1257010.

The product of its digits is 18432, while the sum is 37.

The square root of 21368881 is about 4622.6486996093. The cubic root of 21368881 is about 277.4984703538.

The spelling of 21368881 in words is "twenty-one million, three hundred sixty-eight thousand, eight hundred eighty-one".