20791981 has 8 divisors (see below), whose sum is σ = 23914880. Its totient is φ = 17707248.

The previous prime is 20791973. The next prime is 20791987. The reversal of 20791981 is 18919702.

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 20791981 - 2³ = 20791973 is a prime.

It is a super-2 number, since 2×20791981² = 864612947808722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20791981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20791987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8361 + ... + 10558.

It is an arithmetic number, because the mean of its divisors is an integer number (2989360).

Almost surely, 2^20791981 is an apocalyptic number.

It is an amenable number.

20791981 is a deficient number, since it is larger than the sum of its proper divisors (3122899).

20791981 is a wasteful number, since it uses less digits than its factorization.

20791981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19083.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 20791981 is about 4559.8224746146. The cubic root of 20791981 is about 274.9784269578.

The spelling of 20791981 in words is "twenty million, seven hundred ninety-one thousand, nine hundred eighty-one".