20942640 has 240 divisors, whose sum is σ = 78343200. Its totient is φ = 4988928.

The previous prime is 20942587. The next prime is 20942641. The reversal of 20942640 is 4624902.

It is a tau number, because it is divible by the number of its divisors (240).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20942641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 354931 + ... + 354989.

It is an arithmetic number, because the mean of its divisors is an integer number (326430).

Almost surely, 2^20942640 is an apocalyptic number.

20942640 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 20942640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39171600).

20942640 is an abundant number, since it is smaller than the sum of its proper divisors (57400560).

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

20942640 is a wasteful number, since it uses less digits than its factorization.

20942640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 20942640 is about 4576.3129263633. The cubic root of 20942640 is about 275.6409951074.

It can be divided in two parts, 209 and 42640, that added together give a square (42849 = 207²).

The spelling of 20942640 in words is "twenty million, nine hundred forty-two thousand, six hundred forty".