21687418 has 16 divisors (see below), whose sum is σ = 33840000. Its totient is φ = 10411632.

The previous prime is 21687373. The next prime is 21687473. The reversal of 21687418 is 81478612.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10603 + ... + 12481.

It is an arithmetic number, because the mean of its divisors is an integer number (2115000).

Almost surely, 2^21687418 is an apocalyptic number.

21687418 is a deficient number, since it is larger than the sum of its proper divisors (12152582).

21687418 is a wasteful number, since it uses less digits than its factorization.

21687418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2109.

The product of its digits is 21504, while the sum is 37.

The square root of 21687418 is about 4656.9751985597. The cubic root of 21687418 is about 278.8705265487.

The spelling of 21687418 in words is "twenty-one million, six hundred eighty-seven thousand, four hundred eighteen".