21107207 has 4 divisors (see below), whose sum is σ = 23026056. Its totient is φ = 19188360.

The previous prime is 21107189. The next prime is 21107209. The reversal of 21107207 is 70270112.

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 21107207 - 2²⁰ = 20058631 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21107209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 959408 + ... + 959429.

It is an arithmetic number, because the mean of its divisors is an integer number (5756514).

Almost surely, 2^21107207 is an apocalyptic number.

21107207 is a deficient number, since it is larger than the sum of its proper divisors (1918849).

21107207 is a wasteful number, since it uses less digits than its factorization.

21107207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1918848.

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 21107207 is about 4594.2580467362. The cubic root of 21107207 is about 276.3611066624.

Adding to 21107207 its reverse (70270112), we get a palindrome (91377319).

The spelling of 21107207 in words is "twenty-one million, one hundred seven thousand, two hundred seven".