21801020 has 48 divisors (see below), whose sum is σ = 47301408. Its totient is φ = 8436480.

The previous prime is 21801019. The next prime is 21801023. The reversal of 21801020 is 2010812.

It is a junction number, because it is equal to n+sod(n) for n = 21800986 and 21801004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21801023) 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 15 ways as a sum of consecutive naturals, for example, 138782 + ... + 138938.

It is an arithmetic number, because the mean of its divisors is an integer number (985446).

Almost surely, 2^21801020 is an apocalyptic number.

21801020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21801020 is an abundant number, since it is smaller than the sum of its proper divisors (25500388).

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

21801020 is a wasteful number, since it uses less digits than its factorization.

21801020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350 (or 348 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 21801020 is about 4669.1562406927. The cubic root of 21801020 is about 279.3566009267.

Adding to 21801020 its reverse (2010812), we get a palindrome (23811832).

The spelling of 21801020 in words is "twenty-one million, eight hundred one thousand, twenty".