21023620 has 12 divisors (see below), whose sum is σ = 44149644. Its totient is φ = 8409440.

The previous prime is 21023599. The next prime is 21023623. The reversal of 21023620 is 2632012.

It can be written as a sum of positive squares in 2 ways, for example, as 6461764 + 14561856 = 2542^2 + 3816^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21023594 and 21023603.

It is not an unprimeable number, because it can be changed into a prime (21023623) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 525571 + ... + 525610.

It is an arithmetic number, because the mean of its divisors is an integer number (3679137).

Almost surely, 2^21023620 is an apocalyptic number.

21023620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21023620 is an abundant number, since it is smaller than the sum of its proper divisors (23126024).

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

21023620 is a wasteful number, since it uses less digits than its factorization.

21023620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1051190 (or 1051188 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21023620 is about 4585.1521239758. The cubic root of 21023620 is about 275.9958166418.

Adding to 21023620 its reverse (2632012), we get a palindrome (23655632).

The spelling of 21023620 in words is "twenty-one million, twenty-three thousand, six hundred twenty".