20997999 has 24 divisors (see below), whose sum is σ = 33398352. Its totient is φ = 12606720.

The previous prime is 20997989. The next prime is 20998007. The reversal of 20997999 is 99979902.

It is not a de Polignac number, because 20997999 - 2¹³ = 20989807 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20997989) 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 23 ways as a sum of consecutive naturals, for example, 10249 + ... + 12125.

It is an arithmetic number, because the mean of its divisors is an integer number (1391598).

Almost surely, 2^20997999 is an apocalyptic number.

20997999 is a deficient number, since it is larger than the sum of its proper divisors (12400353).

20997999 is a wasteful number, since it uses less digits than its factorization.

20997999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2007 (or 2004 counting only the distinct ones).

The product of its (nonzero) digits is 826686, while the sum is 54.

The square root of 20997999 is about 4582.3573627556. The cubic root of 20997999 is about 275.8836544911.

The spelling of 20997999 in words is "twenty million, nine hundred ninety-seven thousand, nine hundred ninety-nine".