21331778 has 16 divisors (see below), whose sum is σ = 34727616. Its totient is φ = 9768720.

The previous prime is 21331777. The next prime is 21331781. The reversal of 21331778 is 87713312.

It is not an unprimeable number, because it can be changed into a prime (21331777) 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 in 7 ways as a sum of consecutive naturals, for example, 275 + ... + 6537.

It is an arithmetic number, because the mean of its divisors is an integer number (2170476).

Almost surely, 2^21331778 is an apocalyptic number.

21331778 is a deficient number, since it is larger than the sum of its proper divisors (13395838).

21331778 is a wasteful number, since it uses less digits than its factorization.

21331778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6409.

The product of its digits is 7056, while the sum is 32.

The square root of 21331778 is about 4618.6337806758. The cubic root of 21331778 is about 277.3377695271.

The spelling of 21331778 in words is "twenty-one million, three hundred thirty-one thousand, seven hundred seventy-eight".