21356743 has 4 divisors (see below), whose sum is σ = 22613040. Its totient is φ = 20100448.

The previous prime is 21356723. The next prime is 21356759. The reversal of 21356743 is 34765312.

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 21356743 - 2⁵ = 21356711 is a prime.

It is a super-2 number, since 2×21356743² = 912220943136098, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21356723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 628123 + ... + 628156.

It is an arithmetic number, because the mean of its divisors is an integer number (5653260).

Almost surely, 2^21356743 is an apocalyptic number.

21356743 is a deficient number, since it is larger than the sum of its proper divisors (1256297).

21356743 is a wasteful number, since it uses less digits than its factorization.

21356743 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1256296.

The product of its digits is 15120, while the sum is 31.

The square root of 21356743 is about 4621.3356294474. The cubic root of 21356743 is about 277.4459186333.

The spelling of 21356743 in words is "twenty-one million, three hundred fifty-six thousand, seven hundred forty-three".