21255207 has 4 divisors (see below), whose sum is σ = 28340280. Its totient is φ = 14170136.

The previous prime is 21255203. The next prime is 21255209. The reversal of 21255207 is 70255212.

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 21255207 - 2² = 21255203 is a prime.

It is a super-2 number, since 2×21255207² = 903567649225698, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255203) 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, 3542532 + ... + 3542537.

It is an arithmetic number, because the mean of its divisors is an integer number (7085070).

Almost surely, 2^21255207 is an apocalyptic number.

21255207 is a deficient number, since it is larger than the sum of its proper divisors (7085073).

21255207 is an equidigital number, since it uses as much as digits as its factorization.

21255207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7085072.

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21255207 is about 4610.3369724999. The cubic root of 21255207 is about 277.0055345200.

The spelling of 21255207 in words is "twenty-one million, two hundred fifty-five thousand, two hundred seven".