20820645 has 40 divisors (see below), whose sum is σ = 37766520. Its totient is φ = 10972800.

The previous prime is 20820617. The next prime is 20820649. The reversal of 20820645 is 54602802.

It can be written as a sum of positive squares in 4 ways, for example, as 10381284 + 10439361 = 3222^2 + 3231^2 .

It is not a de Polignac number, because 20820645 - 2¹¹ = 20818597 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20820649) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 40651 + ... + 41159.

It is an arithmetic number, because the mean of its divisors is an integer number (944163).

Almost surely, 2^20820645 is an apocalyptic number.

It is an amenable number.

20820645 is a deficient number, since it is larger than the sum of its proper divisors (16945875).

20820645 is a wasteful number, since it uses less digits than its factorization.

20820645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 627 (or 618 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 20820645 is about 4562.9644969033. The cubic root of 20820645 is about 275.1047314587.

The spelling of 20820645 in words is "twenty million, eight hundred twenty thousand, six hundred forty-five".