20638340 has 48 divisors (see below), whose sum is σ = 46421424. Its totient is φ = 7680000.

The previous prime is 20638339. The next prime is 20638349. The reversal of 20638340 is 4383602.

It can be written as a sum of positive squares in 8 ways, for example, as 5769604 + 14868736 = 2402^2 + 3856^2 .

It is a Smith number, since the sum of its digits (26) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (20638349) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34040 + ... + 34640.

It is an arithmetic number, because the mean of its divisors is an integer number (967113).

Almost surely, 2^20638340 is an apocalyptic number.

20638340 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 20638340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23210712).

20638340 is an abundant number, since it is smaller than the sum of its proper divisors (25783084).

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

20638340 is a wasteful number, since it uses less digits than its factorization.

20638340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728 (or 726 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 26.

The square root of 20638340 is about 4542.9439794037. The cubic root of 20638340 is about 274.2994399857.

The spelling of 20638340 in words is "twenty million, six hundred thirty-eight thousand, three hundred forty".