21891206 has 8 divisors (see below), whose sum is σ = 34768440. Its totient is φ = 10301728.

The previous prime is 21891203. The next prime is 21891209. The reversal of 21891206 is 60219812.

It is an interprime number because it is at equal distance from previous prime (21891203) and next prime (21891209).

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21891203) 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, 321896 + ... + 321963.

It is an arithmetic number, because the mean of its divisors is an integer number (4346055).

Almost surely, 2^21891206 is an apocalyptic number.

21891206 is a deficient number, since it is larger than the sum of its proper divisors (12877234).

21891206 is a wasteful number, since it uses less digits than its factorization.

21891206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 643878.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21891206 is about 4678.8039069831. The cubic root of 21891206 is about 279.7412831310.

The spelling of 21891206 in words is "twenty-one million, eight hundred ninety-one thousand, two hundred six".