21205967 has 4 divisors (see below), whose sum is σ = 21254280. Its totient is φ = 21157656.

The previous prime is 21205927. The next prime is 21205973. The reversal of 21205967 is 76950212.

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 21205967 - 2²⁰ = 20157391 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 (21205927) 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, 23492 + ... + 24377.

It is an arithmetic number, because the mean of its divisors is an integer number (5313570).

Almost surely, 2^21205967 is an apocalyptic number.

21205967 is a deficient number, since it is larger than the sum of its proper divisors (48313).

21205967 is an equidigital number, since it uses as much as digits as its factorization.

21205967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48312.

The product of its (nonzero) digits is 7560, while the sum is 32.

The square root of 21205967 is about 4604.9937024930. The cubic root of 21205967 is about 276.7914646412.

The spelling of 21205967 in words is "twenty-one million, two hundred five thousand, nine hundred sixty-seven".