21239205 has 64 divisors (see below), whose sum is σ = 39916800. Its totient is φ = 9547776.

The previous prime is 21239203. The next prime is 21239237. The reversal of 21239205 is 50293212.

It is not a de Polignac number, because 21239205 - 2¹ = 21239203 is a prime.

It is a super-2 number, since 2×21239205² = 902207658064050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21239203) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 142471 + ... + 142619.

It is an arithmetic number, because the mean of its divisors is an integer number (623700).

Almost surely, 2^21239205 is an apocalyptic number.

It is an amenable number.

21239205 is a deficient number, since it is larger than the sum of its proper divisors (18677595).

21239205 is a wasteful number, since it uses less digits than its factorization.

21239205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 230.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21239205 is about 4608.6011977606. The cubic root of 21239205 is about 276.9360024534.

The spelling of 21239205 in words is "twenty-one million, two hundred thirty-nine thousand, two hundred five".