20997587 has 4 divisors (see below), whose sum is σ = 22612800. Its totient is φ = 19382376.

The previous prime is 20997583. The next prime is 20997619. The reversal of 20997587 is 78579902.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 20997587 - 2² = 20997583 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20997583) 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 3 ways as a sum of consecutive naturals, for example, 807587 + ... + 807612.

It is an arithmetic number, because the mean of its divisors is an integer number (5653200).

Almost surely, 2^20997587 is an apocalyptic number.

20997587 is a deficient number, since it is larger than the sum of its proper divisors (1615213).

20997587 is a wasteful number, since it uses less digits than its factorization.

20997587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1615212.

The product of its (nonzero) digits is 317520, while the sum is 47.

The square root of 20997587 is about 4582.3124075078. The cubic root of 20997587 is about 275.8818501158.

The spelling of 20997587 in words is "twenty million, nine hundred ninety-seven thousand, five hundred eighty-seven".