21111020 has 48 divisors (see below), whose sum is σ = 51202368. Its totient is φ = 7161600.

The previous prime is 21111007. The next prime is 21111029. The reversal of 21111020 is 2011112.

It is a junction number, because it is equal to n+sod(n) for n = 21110989 and 21111007.

It is not an unprimeable number, because it can be changed into a prime (21111029) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13394 + ... + 14886.

It is an arithmetic number, because the mean of its divisors is an integer number (1066716).

Almost surely, 2^21111020 is an apocalyptic number.

21111020 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 21111020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25601184).

21111020 is an abundant number, since it is smaller than the sum of its proper divisors (30091348).

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

21111020 is a wasteful number, since it uses less digits than its factorization.

21111020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1610 (or 1608 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 21111020 is about 4594.6730025106. The cubic root of 21111020 is about 276.3777471311.

Adding to 21111020 its reverse (2011112), we get a palindrome (23122132).

The spelling of 21111020 in words is "twenty-one million, one hundred eleven thousand, twenty".