21865807 has 2 divisors, whose sum is σ = 21865808. Its totient is φ = 21865806.

The previous prime is 21865783. The next prime is 21865829. The reversal of 21865807 is 70856812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21865807 - 2¹¹ = 21863759 is a prime.

It is a super-2 number, since 2×21865807² = 956227031522498, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21865007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932903 + 10932904.

It is an arithmetic number, because the mean of its divisors is an integer number (10932904).

Almost surely, 2^21865807 is an apocalyptic number.

21865807 is a deficient number, since it is larger than the sum of its proper divisors (1).

21865807 is an equidigital number, since it uses as much as digits as its factorization.

21865807 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26880, while the sum is 37.

The square root of 21865807 is about 4676.0888571540. The cubic root of 21865807 is about 279.6330524788.

The spelling of 21865807 in words is "twenty-one million, eight hundred sixty-five thousand, eight hundred seven".