21320020 has 12 divisors (see below), whose sum is σ = 44772084. Its totient is φ = 8528000.

The previous prime is 21319997. The next prime is 21320021. The reversal of 21320020 is 2002312.

It can be written as a sum of positive squares in 2 ways, for example, as 14837904 + 6482116 = 3852^2 + 2546^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21319979 and 21320006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320021) 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, 532981 + ... + 533020.

It is an arithmetic number, because the mean of its divisors is an integer number (3731007).

Almost surely, 2^21320020 is an apocalyptic number.

21320020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21320020 is an abundant number, since it is smaller than the sum of its proper divisors (23452064).

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

21320020 is a wasteful number, since it uses less digits than its factorization.

21320020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1066010 (or 1066008 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 10.

The square root of 21320020 is about 4617.3607179860. The cubic root of 21320020 is about 277.2868042986.

Adding to 21320020 its reverse (2002312), we get a palindrome (23322332).

The spelling of 21320020 in words is "twenty-one million, three hundred twenty thousand, twenty".