20781191 has 16 divisors (see below), whose sum is σ = 23224320. Its totient is φ = 18503040.

The previous prime is 20781181. The next prime is 20781199. The reversal of 20781191 is 19118702.

It is a cyclic number.

It is not a de Polignac number, because 20781191 - 2¹⁸ = 20519047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20781199) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24350 + ... + 25188.

It is an arithmetic number, because the mean of its divisors is an integer number (1451520).

Almost surely, 2^20781191 is an apocalyptic number.

20781191 is a deficient number, since it is larger than the sum of its proper divisors (2443129).

20781191 is a wasteful number, since it uses less digits than its factorization.

20781191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 934.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 20781191 is about 4558.6391609778. The cubic root of 20781191 is about 274.9308520359.

Adding to 20781191 its reverse (19118702), we get a palindrome (39899893).

The spelling of 20781191 in words is "twenty million, seven hundred eighty-one thousand, one hundred ninety-one".