20609640 has 80 divisors (see below), whose sum is σ = 69282180. Its totient is φ = 5495040.

The previous prime is 20609639. The next prime is 20609653. The reversal of 20609640 is 4690602.

It can be written as a sum of positive squares in 2 ways, for example, as 19766916 + 842724 = 4446^2 + 918^2 .

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

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 60 + ... + 6420.

Almost surely, 2^20609640 is an apocalyptic number.

20609640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20609640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34641090).

20609640 is an abundant number, since it is smaller than the sum of its proper divisors (48672540).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20609640 is a wasteful number, since it uses less digits than its factorization.

20609640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6384 (or 6371 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 20609640 is about 4539.7841358373. The cubic root of 20609640 is about 274.1722326310.

The spelling of 20609640 in words is "twenty million, six hundred nine thousand, six hundred forty".