21999967 has 8 divisors (see below), whose sum is σ = 25263360. Its totient is φ = 18947160.

The previous prime is 21999917. The next prime is 21999973. The reversal of 21999967 is 76999912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21999967 - 2⁷ = 21999839 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 (21999907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 52423 + ... + 52840.

It is an arithmetic number, because the mean of its divisors is an integer number (3157920).

Almost surely, 2^21999967 is an apocalyptic number.

21999967 is a deficient number, since it is larger than the sum of its proper divisors (3263393).

21999967 is a wasteful number, since it uses less digits than its factorization.

21999967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105293.

The product of its digits is 551124, while the sum is 52.

The square root of 21999967 is about 4690.4122420103. The cubic root of 21999967 is about 280.2037929635.

Subtracting 21999967 from its reverse (76999912), we obtain a palindrome (54999945).

The spelling of 21999967 in words is "twenty-one million, nine hundred ninety-nine thousand, nine hundred sixty-seven".