21105207 has 24 divisors (see below), whose sum is σ = 31853120. Its totient is φ = 13452480.

The previous prime is 21105199. The next prime is 21105221. The reversal of 21105207 is 70250112.

It is not a de Polignac number, because 21105207 - 2³ = 21105199 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21105207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105107) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19794 + ... + 20832.

Almost surely, 2^21105207 is an apocalyptic number.

21105207 is a deficient number, since it is larger than the sum of its proper divisors (10747913).

21105207 is a wasteful number, since it uses less digits than its factorization.

21105207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1143 (or 1140 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21105207 is about 4594.0403785774. The cubic root of 21105207 is about 276.3523775796.

Adding to 21105207 its reverse (70250112), we get a palindrome (91355319).

It can be divided in two parts, 21105 and 207, that added together give a palindrome (21312).

The spelling of 21105207 in words is "twenty-one million, one hundred five thousand, two hundred seven".