20521601 has 8 divisors (see below), whose sum is σ = 21809160. Its totient is φ = 19309824.

The previous prime is 20521583. The next prime is 20521603. The reversal of 20521601 is 10612502.

It can be written as a sum of positive squares in 4 ways, for example, as 8439025 + 12082576 = 2905^2 + 3476^2 .

It is not a de Polignac number, because 20521601 - 2¹⁴ = 20505217 is a prime.

It is a super-2 number, since 2×20521601² = 842272215206402, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20521601.

It is not an unprimeable number, because it can be changed into a prime (20521603) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2825 + ... + 7001.

It is an arithmetic number, because the mean of its divisors is an integer number (2726145).

Almost surely, 2^20521601 is an apocalyptic number.

It is an amenable number.

20521601 is a deficient number, since it is larger than the sum of its proper divisors (1287559).

20521601 is an frugal number, since it uses more digits than its factorization.

20521601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4228 (or 4194 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 20521601 is about 4530.0773724077. The cubic root of 20521601 is about 273.7812780230.

Subtracting from 20521601 its reverse (10612502), we obtain a palindrome (9909099).

The spelling of 20521601 in words is "twenty million, five hundred twenty-one thousand, six hundred one".