21398687 has 2 divisors, whose sum is σ = 21398688. Its totient is φ = 21398686.

The previous prime is 21398683. The next prime is 21398701. The reversal of 21398687 is 78689312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21398687 - 2² = 21398683 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21398683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699343 + 10699344.

It is an arithmetic number, because the mean of its divisors is an integer number (10699344).

Almost surely, 2^21398687 is an apocalyptic number.

21398687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398687 is an equidigital number, since it uses as much as digits as its factorization.

21398687 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 44.

The square root of 21398687 is about 4625.8714854609. The cubic root of 21398687 is about 277.6274316656.

The spelling of 21398687 in words is "twenty-one million, three hundred ninety-eight thousand, six hundred eighty-seven".