21099967 has 4 divisors (see below), whose sum is σ = 24114256. Its totient is φ = 18085680.

The previous prime is 21099959. The next prime is 21099973. The reversal of 21099967 is 76999012.

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 21099967 - 2³ = 21099959 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 (21099917) 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, 1507134 + ... + 1507147.

It is an arithmetic number, because the mean of its divisors is an integer number (6028564).

Almost surely, 2^21099967 is an apocalyptic number.

21099967 is a deficient number, since it is larger than the sum of its proper divisors (3014289).

21099967 is an equidigital number, since it uses as much as digits as its factorization.

21099967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3014288.

The product of its (nonzero) digits is 61236, while the sum is 43.

The square root of 21099967 is about 4593.4700390881. The cubic root of 21099967 is about 276.3295047673.

The spelling of 21099967 in words is "twenty-one million, ninety-nine thousand, nine hundred sixty-seven".