21191678 has 4 divisors (see below), whose sum is σ = 31787520. Its totient is φ = 10595838.

The previous prime is 21191659. The next prime is 21191699. The reversal of 21191678 is 87619112.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5297918 + ... + 5297921.

It is an arithmetic number, because the mean of its divisors is an integer number (7946880).

Almost surely, 2^21191678 is an apocalyptic number.

21191678 is a deficient number, since it is larger than the sum of its proper divisors (10595842).

21191678 is a wasteful number, since it uses less digits than its factorization.

21191678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10595841.

The product of its digits is 6048, while the sum is 35.

The square root of 21191678 is about 4603.4419731327. The cubic root of 21191678 is about 276.7292814846.

The spelling of 21191678 in words is "twenty-one million, one hundred ninety-one thousand, six hundred seventy-eight".