20631640 has 32 divisors (see below), whose sum is σ = 47016000. Its totient is φ = 8146944.

The previous prime is 20631619. The next prime is 20631641. The reversal of 20631640 is 4613602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20631641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 105 + ... + 6424.

It is an arithmetic number, because the mean of its divisors is an integer number (1469250).

Almost surely, 2^20631640 is an apocalyptic number.

20631640 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 20631640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23508000).

20631640 is an abundant number, since it is smaller than the sum of its proper divisors (26384360).

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

20631640 is a wasteful number, since it uses less digits than its factorization.

20631640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6619 (or 6615 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 22.

The square root of 20631640 is about 4542.2065122581. The cubic root of 20631640 is about 274.2697540523.

The spelling of 20631640 in words is "twenty million, six hundred thirty-one thousand, six hundred forty".