20717891 has 8 divisors (see below), whose sum is σ = 21450240. Its totient is φ = 19994688.

The previous prime is 20717869. The next prime is 20717897. The reversal of 20717891 is 19871702.

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 20717891 - 2²² = 16523587 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20717897) 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, 2495 + ... + 6903.

It is an arithmetic number, because the mean of its divisors is an integer number (2681280).

Almost surely, 2^20717891 is an apocalyptic number.

20717891 is a deficient number, since it is larger than the sum of its proper divisors (732349).

20717891 is a wasteful number, since it uses less digits than its factorization.

20717891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4573.

The product of its (nonzero) digits is 7056, while the sum is 35.

The square root of 20717891 is about 4551.6910044510. The cubic root of 20717891 is about 274.6514194951.

The spelling of 20717891 in words is "twenty million, seven hundred seventeen thousand, eight hundred ninety-one".