21284387 has 2 divisors, whose sum is σ = 21284388. Its totient is φ = 21284386.

The previous prime is 21284381. The next prime is 21284401. The reversal of 21284387 is 78348212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21284387 - 2²⁰ = 20235811 is a prime.

It is not a weakly prime, because it can be changed into another prime (21284381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10642193 + 10642194.

It is an arithmetic number, because the mean of its divisors is an integer number (10642194).

Almost surely, 2^21284387 is an apocalyptic number.

21284387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21284387 is an equidigital number, since it uses as much as digits as its factorization.

21284387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21504, while the sum is 35.

The square root of 21284387 is about 4613.5005147935. The cubic root of 21284387 is about 277.1322379895.

The spelling of 21284387 in words is "twenty-one million, two hundred eighty-four thousand, three hundred eighty-seven".