21369643 has 4 divisors (see below), whose sum is σ = 21384448. Its totient is φ = 21354840.

The previous prime is 21369617. The next prime is 21369659. The reversal of 21369643 is 34696312.

It is a happy number.

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 21369643 - 2¹⁷ = 21238571 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21369599 and 21369608.

It is not an unprimeable number, because it can be changed into a prime (21369043) 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, 4971 + ... + 8212.

It is an arithmetic number, because the mean of its divisors is an integer number (5346112).

Almost surely, 2^21369643 is an apocalyptic number.

21369643 is a deficient number, since it is larger than the sum of its proper divisors (14805).

21369643 is a wasteful number, since it uses less digits than its factorization.

21369643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14804.

The product of its digits is 23328, while the sum is 34.

The square root of 21369643 is about 4622.7311191546. The cubic root of 21369643 is about 277.5017687845.

It can be divided in two parts, 21 and 369643, that added together give a square (369664 = 608²).

The spelling of 21369643 in words is "twenty-one million, three hundred sixty-nine thousand, six hundred forty-three".