20116991 has 8 divisors (see below), whose sum is σ = 21669120. Its totient is φ = 18614232.

The previous prime is 20116979. The next prime is 20116997. The reversal of 20116991 is 19961102.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20116991 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20116997) 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, 11495 + ... + 13128.

It is an arithmetic number, because the mean of its divisors is an integer number (2708640).

Almost surely, 2^20116991 is an apocalyptic number.

20116991 is a deficient number, since it is larger than the sum of its proper divisors (1552129).

20116991 is a wasteful number, since it uses less digits than its factorization.

20116991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24685.

The product of its (nonzero) digits is 972, while the sum is 29.

The square root of 20116991 is about 4485.1968741628. The cubic root of 20116991 is about 271.9700037207.

It can be divided in two parts, 201 and 16991, that multiplied together give a triangular number (3415191 = T₂₆₁₃).

The spelling of 20116991 in words is "twenty million, one hundred sixteen thousand, nine hundred ninety-one".