21642881 has 8 divisors (see below), whose sum is σ = 24534720. Its totient is φ = 18926352.

The previous prime is 21642871. The next prime is 21642883. The reversal of 21642881 is 18824612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21642881 - 2¹⁴ = 21626497 is a prime.

It is a super-2 number, since 2×21642881² = 936828595960322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21642883) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43565 + ... + 44058.

It is an arithmetic number, because the mean of its divisors is an integer number (3066840).

Almost surely, 2^21642881 is an apocalyptic number.

It is an amenable number.

21642881 is a deficient number, since it is larger than the sum of its proper divisors (2891839).

21642881 is a wasteful number, since it uses less digits than its factorization.

21642881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87655.

The product of its digits is 6144, while the sum is 32.

The square root of 21642881 is about 4652.1909892007. The cubic root of 21642881 is about 278.6795007622.

The spelling of 21642881 in words is "twenty-one million, six hundred forty-two thousand, eight hundred eighty-one".