21879643 has 2 divisors, whose sum is σ = 21879644. Its totient is φ = 21879642.

The previous prime is 21879631. The next prime is 21879661. The reversal of 21879643 is 34697812.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21879643 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21879596 and 21879605.

It is not a weakly prime, because it can be changed into another prime (21879043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10939821 + 10939822.

It is an arithmetic number, because the mean of its divisors is an integer number (10939822).

Almost surely, 2^21879643 is an apocalyptic number.

21879643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21879643 is an equidigital number, since it uses as much as digits as its factorization.

21879643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 21879643 is about 4677.5680647105. The cubic root of 21879643 is about 279.6920210644.

It can be divided in two parts, 21879 and 643, that added together give a palindrome (22522).

The spelling of 21879643 in words is "twenty-one million, eight hundred seventy-nine thousand, six hundred forty-three".