21916387 has 2 divisors, whose sum is σ = 21916388. Its totient is φ = 21916386.

The previous prime is 21916381. The next prime is 21916393. The reversal of 21916387 is 78361912.

It is a balanced prime because it is at equal distance from previous prime (21916381) and next prime (21916393).

It is a cyclic number.

It is not a de Polignac number, because 21916387 - 2³ = 21916379 is a prime.

It is not a weakly prime, because it can be changed into another prime (21916381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10958193 + 10958194.

It is an arithmetic number, because the mean of its divisors is an integer number (10958194).

Almost surely, 2^21916387 is an apocalyptic number.

21916387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21916387 is an equidigital number, since it uses as much as digits as its factorization.

21916387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 21916387 is about 4681.4940991098. The cubic root of 21916387 is about 279.8485022285.

The spelling of 21916387 in words is "twenty-one million, nine hundred sixteen thousand, three hundred eighty-seven".