21687395 has 4 divisors (see below), whose sum is σ = 26024880. Its totient is φ = 17349912.

The previous prime is 21687373. The next prime is 21687473. The reversal of 21687395 is 59378612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21687395 - 2¹⁸ = 21425251 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2168735 + ... + 2168744.

It is an arithmetic number, because the mean of its divisors is an integer number (6506220).

Almost surely, 2^21687395 is an apocalyptic number.

21687395 is a deficient number, since it is larger than the sum of its proper divisors (4337485).

21687395 is an equidigital number, since it uses as much as digits as its factorization.

21687395 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4337484.

The product of its digits is 90720, while the sum is 41.

The square root of 21687395 is about 4656.9727291450. The cubic root of 21687395 is about 278.8704279658.

The spelling of 21687395 in words is "twenty-one million, six hundred eighty-seven thousand, three hundred ninety-five".