21678006 has 32 divisors (see below), whose sum is σ = 51706368. Its totient is φ = 5924160.

The previous prime is 21678001. The next prime is 21678037. The reversal of 21678006 is 60087612.

It is a happy number.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21678001) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10255 + ... + 12186.

It is an arithmetic number, because the mean of its divisors is an integer number (1615824).

Almost surely, 2^21678006 is an apocalyptic number.

21678006 is an abundant number, since it is smaller than the sum of its proper divisors (30028362).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21678006 is a wasteful number, since it uses less digits than its factorization.

21678006 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22476.

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 21678006 is about 4655.9645617208. The cubic root of 21678006 is about 278.8301788966.

The spelling of 21678006 in words is "twenty-one million, six hundred seventy-eight thousand, six".