21385743 has 4 divisors (see below), whose sum is σ = 28514328. Its totient is φ = 14257160.

The previous prime is 21385733. The next prime is 21385757. The reversal of 21385743 is 34758312.

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

It is a cyclic number.

It is not a de Polignac number, because 21385743 - 2¹⁰ = 21384719 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3564288 + ... + 3564293.

It is an arithmetic number, because the mean of its divisors is an integer number (7128582).

Almost surely, 2^21385743 is an apocalyptic number.

21385743 is a deficient number, since it is larger than the sum of its proper divisors (7128585).

21385743 is an equidigital number, since it uses as much as digits as its factorization.

21385743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7128584.

The product of its digits is 20160, while the sum is 33.

The square root of 21385743 is about 4624.4721860986. The cubic root of 21385743 is about 277.5714417147.

The spelling of 21385743 in words is "twenty-one million, three hundred eighty-five thousand, seven hundred forty-three".