21128678 has 8 divisors (see below), whose sum is σ = 31820040. Its totient is φ = 10522000.

The previous prime is 21128659. The next prime is 21128683. The reversal of 21128678 is 87682112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20543 + ... + 21546.

It is an arithmetic number, because the mean of its divisors is an integer number (3977505).

Almost surely, 2^21128678 is an apocalyptic number.

21128678 is a deficient number, since it is larger than the sum of its proper divisors (10691362).

21128678 is a wasteful number, since it uses less digits than its factorization.

21128678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42342.

The product of its digits is 10752, while the sum is 35.

The square root of 21128678 is about 4596.5941739510. The cubic root of 21128678 is about 276.4547830143.

The spelling of 21128678 in words is "twenty-one million, one hundred twenty-eight thousand, six hundred seventy-eight".