20997549 has 10 divisors (see below), whose sum is σ = 31366830. Its totient is φ = 13998312.

The previous prime is 20997541. The next prime is 20997553. The reversal of 20997549 is 94579902.

It can be written as a sum of positive squares in only one way, i.e., 20412324 + 585225 = 4518^2 + 765^2 .

It is not a de Polignac number, because 20997549 - 2³ = 20997541 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20997541) 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 9 ways as a sum of consecutive naturals, for example, 129534 + ... + 129695.

It is an arithmetic number, because the mean of its divisors is an integer number (3136683).

Almost surely, 2^20997549 is an apocalyptic number.

It is an amenable number.

20997549 is a deficient number, since it is larger than the sum of its proper divisors (10369281).

20997549 is an equidigital number, since it uses as much as digits as its factorization.

20997549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 259241 (or 259232 counting only the distinct ones).

The product of its (nonzero) digits is 204120, while the sum is 45.

The square root of 20997549 is about 4582.3082611278. The cubic root of 20997549 is about 275.8816836917.

The spelling of 20997549 in words is "twenty million, nine hundred ninety-seven thousand, five hundred forty-nine".