21211020 has 36 divisors (see below), whose sum is σ = 64340640. Its totient is φ = 5656224.

The previous prime is 21211013. The next prime is 21211033. The reversal of 21211020 is 2011212.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21210993 and 21211011.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 58740 + ... + 59099.

It is an arithmetic number, because the mean of its divisors is an integer number (1787240).

Almost surely, 2^21211020 is an apocalyptic number.

21211020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21211020 is an abundant number, since it is smaller than the sum of its proper divisors (43129620).

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

21211020 is a wasteful number, since it uses less digits than its factorization.

21211020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117854 (or 117849 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21211020 is about 4605.5423133438. The cubic root of 21211020 is about 276.8134477022.

Adding to 21211020 its reverse (2011212), we get a palindrome (23222232).

The spelling of 21211020 in words is "twenty-one million, two hundred eleven thousand, twenty".