21778814 has 4 divisors (see below), whose sum is σ = 32668224. Its totient is φ = 10889406.

The previous prime is 21778811. The next prime is 21778817. The reversal of 21778814 is 41887712.

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

It is an interprime number because it is at equal distance from previous prime (21778811) and next prime (21778817).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21778811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5444702 + ... + 5444705.

It is an arithmetic number, because the mean of its divisors is an integer number (8167056).

Almost surely, 2^21778814 is an apocalyptic number.

21778814 is a deficient number, since it is larger than the sum of its proper divisors (10889410).

21778814 is a wasteful number, since it uses less digits than its factorization.

21778814 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10889409.

The product of its digits is 25088, while the sum is 38.

The square root of 21778814 is about 4666.7776891555. Note that the first 3 decimals coincide. The cubic root of 21778814 is about 279.2617200437.

The spelling of 21778814 in words is "twenty-one million, seven hundred seventy-eight thousand, eight hundred fourteen".