20321645 has 4 divisors (see below), whose sum is σ = 24385980. Its totient is φ = 16257312.

The previous prime is 20321641. The next prime is 20321657. The reversal of 20321645 is 54612302.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54612302 = 2 ⋅27306151.

It can be written as a sum of positive squares in 2 ways, for example, as 3396649 + 16924996 = 1843^2 + 4114^2 .

It is a cyclic number.

It is not a de Polignac number, because 20321645 - 2² = 20321641 is a prime.

It is a super-3 number, since 3×20321645³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20321645.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20321641) 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 3 ways as a sum of consecutive naturals, for example, 2032160 + ... + 2032169.

It is an arithmetic number, because the mean of its divisors is an integer number (6096495).

Almost surely, 2^20321645 is an apocalyptic number.

It is an amenable number.

20321645 is a deficient number, since it is larger than the sum of its proper divisors (4064335).

20321645 is an equidigital number, since it uses as much as digits as its factorization.

20321645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4064334.

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 20321645 is about 4507.9535268235. The cubic root of 20321645 is about 272.8891614441.

Adding to 20321645 its reverse (54612302), we get a palindrome (74933947).

The spelling of 20321645 in words is "twenty million, three hundred twenty-one thousand, six hundred forty-five".