20791521 has 24 divisors (see below), whose sum is σ = 31922280. Its totient is φ = 13015296.

The previous prime is 20791513. The next prime is 20791523. The reversal of 20791521 is 12519702.

It can be written as a sum of positive squares in 4 ways, for example, as 2822400 + 17969121 = 1680^2 + 4239^2 .

It is not a de Polignac number, because 20791521 - 2³ = 20791513 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20791523) 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 23 ways as a sum of consecutive naturals, for example, 8581 + ... + 10733.

It is an arithmetic number, because the mean of its divisors is an integer number (1330095).

Almost surely, 2^20791521 is an apocalyptic number.

It is an amenable number.

20791521 is a deficient number, since it is larger than the sum of its proper divisors (11130759).

20791521 is a wasteful number, since it uses less digits than its factorization.

20791521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2225 (or 2222 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 20791521 is about 4559.7720337754. The cubic root of 20791521 is about 274.9763990765.

It can be divided in two parts, 207915 and 21, that added together give a square (207936 = 456²).

The spelling of 20791521 in words is "twenty million, seven hundred ninety-one thousand, five hundred twenty-one".