20997091 has 16 divisors (see below), whose sum is σ = 23514624. Its totient is φ = 18646144.

The previous prime is 20997059. The next prime is 20997101. The reversal of 20997091 is 19079902.

It is not a de Polignac number, because 20997091 - 2⁵ = 20997059 is a prime.

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 20997091.

It is not an unprimeable number, because it can be changed into a prime (20997491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32130 + ... + 32776.

It is an arithmetic number, because the mean of its divisors is an integer number (1469664).

Almost surely, 2^20997091 is an apocalyptic number.

20997091 is a deficient number, since it is larger than the sum of its proper divisors (2517533).

20997091 is a wasteful number, since it uses less digits than its factorization.

20997091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 770.

The product of its (nonzero) digits is 10206, while the sum is 37.

The square root of 20997091 is about 4582.2582860419. The cubic root of 20997091 is about 275.8796778269.

The spelling of 20997091 in words is "twenty million, nine hundred ninety-seven thousand, ninety-one".