21199967 has 4 divisors (see below), whose sum is σ = 21209496. Its totient is φ = 21190440.

The previous prime is 21199949. The next prime is 21199973. The reversal of 21199967 is 76999112.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21199967 - 2¹⁰ = 21198943 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 (21192967) 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, 548 + ... + 6534.

It is an arithmetic number, because the mean of its divisors is an integer number (5302374).

Almost surely, 2^21199967 is an apocalyptic number.

21199967 is a deficient number, since it is larger than the sum of its proper divisors (9529).

21199967 is an equidigital number, since it uses as much as digits as its factorization.

21199967 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9528.

The product of its digits is 61236, while the sum is 44.

The square root of 21199967 is about 4604.3421897161. The cubic root of 21199967 is about 276.7653571241.

The spelling of 21199967 in words is "twenty-one million, one hundred ninety-nine thousand, nine hundred sixty-seven".