20805642 has 96 divisors (see below), whose sum is σ = 54250560. Its totient is φ = 5679360.

The previous prime is 20805623. The next prime is 20805643. The reversal of 20805642 is 24650802.

20805642 is a `hidden beast` number, since 20 + 80 + 564 + 2 = 666.

It is not an unprimeable number, because it can be changed into a prime (20805643) 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, 151798 + ... + 151934.

It is an arithmetic number, because the mean of its divisors is an integer number (565110).

Almost surely, 2^20805642 is an apocalyptic number.

20805642 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 20805642, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27125280).

20805642 is an abundant number, since it is smaller than the sum of its proper divisors (33444918).

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

20805642 is a wasteful number, since it uses less digits than its factorization.

20805642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 228 (or 225 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 20805642 is about 4561.3202036253. The cubic root of 20805642 is about 275.0386369956.

The spelling of 20805642 in words is "twenty million, eight hundred five thousand, six hundred forty-two".