20735991 has 6 divisors (see below), whose sum is σ = 29952000. Its totient is φ = 13823988.

The previous prime is 20735969. The next prime is 20736017. The reversal of 20735991 is 19953702.

It is not a de Polignac number, because 20735991 - 2⁶ = 20735927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20735191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1151991 + ... + 1152008.

It is an arithmetic number, because the mean of its divisors is an integer number (4992000).

Almost surely, 2^20735991 is an apocalyptic number.

20735991 is a deficient number, since it is larger than the sum of its proper divisors (9216009).

20735991 is a wasteful number, since it uses less digits than its factorization.

20735991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2304005 (or 2304002 counting only the distinct ones).

The product of its (nonzero) digits is 17010, while the sum is 36.

The square root of 20735991 is about 4553.6788424306. The cubic root of 20735991 is about 274.7313784658.

It can be divided in two parts, 2073599 and 1, that added together give a square (2073600 = 1440²).

The spelling of 20735991 in words is "twenty million, seven hundred thirty-five thousand, nine hundred ninety-one".