21878887 has 2 divisors, whose sum is σ = 21878888. Its totient is φ = 21878886.

The previous prime is 21878869. The next prime is 21878893. The reversal of 21878887 is 78887812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21878887 - 2¹¹ = 21876839 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21878887.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21878827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10939443 + 10939444.

It is an arithmetic number, because the mean of its divisors is an integer number (10939444).

Almost surely, 2^21878887 is an apocalyptic number.

21878887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21878887 is an equidigital number, since it uses as much as digits as its factorization.

21878887 is an evil number, because the sum of its binary digits is even.

The product of its digits is 401408, while the sum is 49.

The square root of 21878887 is about 4677.4872527886. The cubic root of 21878887 is about 279.6887996590.

The spelling of 21878887 in words is "twenty-one million, eight hundred seventy-eight thousand, eight hundred eighty-seven".