21881287 has 2 divisors, whose sum is σ = 21881288. Its totient is φ = 21881286.

The previous prime is 21881269. The next prime is 21881297. The reversal of 21881287 is 78218812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21881287 - 2¹¹ = 21879239 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21881297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10940643 + 10940644.

It is an arithmetic number, because the mean of its divisors is an integer number (10940644).

Almost surely, 2^21881287 is an apocalyptic number.

21881287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21881287 is an equidigital number, since it uses as much as digits as its factorization.

21881287 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14336, while the sum is 37.

The square root of 21881287 is about 4677.7437937536. The cubic root of 21881287 is about 279.6990260868.

The spelling of 21881287 in words is "twenty-one million, eight hundred eighty-one thousand, two hundred eighty-seven".