21071807 has 2 divisors, whose sum is σ = 21071808. Its totient is φ = 21071806.

The previous prime is 21071803. The next prime is 21071819. The reversal of 21071807 is 70817012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21071807 - 2² = 21071803 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21071801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10535903 + 10535904.

It is an arithmetic number, because the mean of its divisors is an integer number (10535904).

Almost surely, 2^21071807 is an apocalyptic number.

21071807 is a deficient number, since it is larger than the sum of its proper divisors (1).

21071807 is an equidigital number, since it uses as much as digits as its factorization.

21071807 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 784, while the sum is 26.

The square root of 21071807 is about 4590.4037948747. The cubic root of 21071807 is about 276.2065203234.

Adding to 21071807 its reverse (70817012), we get a palindrome (91888819).

The spelling of 21071807 in words is "twenty-one million, seventy-one thousand, eight hundred seven".