21745234 has 16 divisors (see below), whose sum is σ = 39240000. Its totient is φ = 8828784.

The previous prime is 21745201. The next prime is 21745247. The reversal of 21745234 is 43254712.

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 7 ways as a sum of consecutive naturals, for example, 40609 + ... + 41140.

It is an arithmetic number, because the mean of its divisors is an integer number (2452500).

Almost surely, 2^21745234 is an apocalyptic number.

21745234 is a deficient number, since it is larger than the sum of its proper divisors (17494766).

21745234 is a wasteful number, since it uses less digits than its factorization.

21745234 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81777.

The product of its digits is 6720, while the sum is 28.

The square root of 21745234 is about 4663.1785297155. The cubic root of 21745234 is about 279.1181182179.

Adding to 21745234 its reverse (43254712), we get a palindrome (64999946).

It can be divided in two parts, 217 and 45234, that added together give a triangular number (45451 = T₃₀₁).

The spelling of 21745234 in words is "twenty-one million, seven hundred forty-five thousand, two hundred thirty-four".