21645743 has 16 divisors (see below), whose sum is σ = 26645760. Its totient is φ = 17160576.

The previous prime is 21645739. The next prime is 21645749. The reversal of 21645743 is 34754612.

It is a cyclic number.

It is not a de Polignac number, because 21645743 - 2² = 21645739 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645749) 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 15 ways as a sum of consecutive naturals, for example, 5480 + ... + 8562.

It is an arithmetic number, because the mean of its divisors is an integer number (1665360).

Almost surely, 2^21645743 is an apocalyptic number.

21645743 is a deficient number, since it is larger than the sum of its proper divisors (5000017).

21645743 is a wasteful number, since it uses less digits than its factorization.

21645743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3166.

The product of its digits is 20160, while the sum is 32.

The square root of 21645743 is about 4652.4985760342. The cubic root of 21645743 is about 278.6917841788.

The spelling of 21645743 in words is "twenty-one million, six hundred forty-five thousand, seven hundred forty-three".