21206438 has 16 divisors (see below), whose sum is σ = 35221824. Its totient is φ = 9494760.

The previous prime is 21206407. The next prime is 21206441. The reversal of 21206438 is 83460212.

It is a super-3 number, since 3×21206438³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5720 + ... + 8667.

It is an arithmetic number, because the mean of its divisors is an integer number (2201364).

Almost surely, 2^21206438 is an apocalyptic number.

21206438 is the 2462-nd centered heptagonal number.

21206438 is a deficient number, since it is larger than the sum of its proper divisors (14015386).

21206438 is a wasteful number, since it uses less digits than its factorization.

21206438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14467.

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 21206438 is about 4605.0448423441. The cubic root of 21206438 is about 276.7935138729.

It can be divided in two parts, 2120 and 6438, that added together give a palindrome (8558).

The spelling of 21206438 in words is "twenty-one million, two hundred six thousand, four hundred thirty-eight".