20993640 has 128 divisors (see below), whose sum is σ = 68584320. Its totient is φ = 5120000.

The previous prime is 20993633. The next prime is 20993663. The reversal of 20993640 is 4639902.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 83515 + ... + 83765.

It is an arithmetic number, because the mean of its divisors is an integer number (535815).

Almost surely, 2^20993640 is an apocalyptic number.

20993640 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 20993640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34292160).

20993640 is an abundant number, since it is smaller than the sum of its proper divisors (47590680).

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

20993640 is a wasteful number, since it uses less digits than its factorization.

20993640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323 (or 319 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 33.

The square root of 20993640 is about 4581.8817095163. The cubic root of 20993640 is about 275.8645628295.

The spelling of 20993640 in words is "twenty million, nine hundred ninety-three thousand, six hundred forty".