21331745 has 16 divisors (see below), whose sum is σ = 26248320. Its totient is φ = 16637184.

The previous prime is 21331729. The next prime is 21331777. The reversal of 21331745 is 54713312.

It is a cyclic number.

It is not a de Polignac number, because 21331745 - 2⁴ = 21331729 is a prime.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 49049 + ... + 49481.

It is an arithmetic number, because the mean of its divisors is an integer number (1640520).

Almost surely, 2^21331745 is an apocalyptic number.

It is an amenable number.

21331745 is a deficient number, since it is larger than the sum of its proper divisors (4916575).

21331745 is a wasteful number, since it uses less digits than its factorization.

21331745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 664.

The product of its digits is 2520, while the sum is 26.

The square root of 21331745 is about 4618.6302081894. The cubic root of 21331745 is about 277.3376265143.

The spelling of 21331745 in words is "twenty-one million, three hundred thirty-one thousand, seven hundred forty-five".