21379943 has 4 divisors (see below), whose sum is σ = 23024568. Its totient is φ = 19735320.

The previous prime is 21379933. The next prime is 21379957. The reversal of 21379943 is 34997312.

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 21379943 - 2⁴ = 21379927 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21379897 and 21379906.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21379913) 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, 822293 + ... + 822318.

It is an arithmetic number, because the mean of its divisors is an integer number (5756142).

Almost surely, 2^21379943 is an apocalyptic number.

21379943 is a deficient number, since it is larger than the sum of its proper divisors (1644625).

21379943 is a wasteful number, since it uses less digits than its factorization.

21379943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1644624.

The product of its digits is 40824, while the sum is 38.

The square root of 21379943 is about 4623.8450449815. The cubic root of 21379943 is about 277.5463461806.

It can be divided in two parts, 21379 and 943, that added together give a palindrome (22322).

The spelling of 21379943 in words is "twenty-one million, three hundred seventy-nine thousand, nine hundred forty-three".