21681118 has 4 divisors (see below), whose sum is σ = 32521680. Its totient is φ = 10840558.

The previous prime is 21681113. The next prime is 21681151. The reversal of 21681118 is 81118612.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5420278 + ... + 5420281.

It is an arithmetic number, because the mean of its divisors is an integer number (8130420).

Almost surely, 2^21681118 is an apocalyptic number.

21681118 is a deficient number, since it is larger than the sum of its proper divisors (10840562).

21681118 is a wasteful number, since it uses less digits than its factorization.

21681118 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10840561.

The product of its digits is 768, while the sum is 28.

The square root of 21681118 is about 4656.2987447113. The cubic root of 21681118 is about 278.8435208064.

The spelling of 21681118 in words is "twenty-one million, six hundred eighty-one thousand, one hundred eighteen".