21208791 has 8 divisors (see below), whose sum is σ = 28543104. Its totient is φ = 14006840.

The previous prime is 21208757. The next prime is 21208813. The reversal of 21208791 is 19780212.

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 21208791 - 2⁶ = 21208727 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21208711) 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, 32715 + ... + 33356.

It is an arithmetic number, because the mean of its divisors is an integer number (3567888).

Almost surely, 2^21208791 is an apocalyptic number.

21208791 is a deficient number, since it is larger than the sum of its proper divisors (7334313).

21208791 is a wasteful number, since it uses less digits than its factorization.

21208791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66181.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21208791 is about 4605.3003159403. The cubic root of 21208791 is about 276.8037508750.

The spelling of 21208791 in words is "twenty-one million, two hundred eight thousand, seven hundred ninety-one".