21239105 has 4 divisors (see below), whose sum is σ = 25486932. Its totient is φ = 16991280.

The previous prime is 21239087. The next prime is 21239173. The reversal of 21239105 is 50193212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16908544 + 4330561 = 4112^2 + 2081^2 .

It is not a de Polignac number, because 21239105 - 2¹² = 21235009 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2123906 + ... + 2123915.

It is an arithmetic number, because the mean of its divisors is an integer number (6371733).

Almost surely, 2^21239105 is an apocalyptic number.

It is an amenable number.

21239105 is a deficient number, since it is larger than the sum of its proper divisors (4247827).

21239105 is an equidigital number, since it uses as much as digits as its factorization.

21239105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4247826.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21239105 is about 4608.5903484688. The cubic root of 21239105 is about 276.9355678225.

It can be divided in two parts, 21 and 239105, that multiplied together give a palindrome (5021205).

The spelling of 21239105 in words is "twenty-one million, two hundred thirty-nine thousand, one hundred five".