21893818 has 4 divisors (see below), whose sum is σ = 32840730. Its totient is φ = 10946908.

The previous prime is 21893813. The next prime is 21893827. The reversal of 21893818 is 81839812.

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

It can be written as a sum of positive squares in only one way, i.e., 21594609 + 299209 = 4647^2 + 547^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21893813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5473453 + ... + 5473456.

Almost surely, 2^21893818 is an apocalyptic number.

21893818 is a deficient number, since it is larger than the sum of its proper divisors (10946912).

21893818 is a wasteful number, since it uses less digits than its factorization.

21893818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10946911.

The product of its digits is 27648, while the sum is 40.

The square root of 21893818 is about 4679.0830298254. The cubic root of 21893818 is about 279.7524086818.

The spelling of 21893818 in words is "twenty-one million, eight hundred ninety-three thousand, eight hundred eighteen".