20815840 has 24 divisors (see below), whose sum is σ = 49177800. Its totient is φ = 8326272.

The previous prime is 20815831. The next prime is 20815853. The reversal of 20815840 is 4851802.

It is a junction number, because it is equal to n+sod(n) for n = 20815799 and 20815808.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64890 + ... + 65209.

It is an arithmetic number, because the mean of its divisors is an integer number (2049075).

Almost surely, 2^20815840 is an apocalyptic number.

20815840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20815840 is an abundant number, since it is smaller than the sum of its proper divisors (28361960).

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

20815840 is a wasteful number, since it uses less digits than its factorization.

20815840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130114 (or 130106 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 28.

The square root of 20815840 is about 4562.4379447835. The cubic root of 20815840 is about 275.0835668897.

It can be divided in two parts, 2081 and 5840, that added together give a square (7921 = 89²).

The spelling of 20815840 in words is "twenty million, eight hundred fifteen thousand, eight hundred forty".