21303720 has 144 divisors (see below), whose sum is σ = 74573460. Its totient is φ = 5256192.

The previous prime is 21303713. The next prime is 21303757. The reversal of 21303720 is 2730312.

It can be written as a sum of positive squares in 2 ways, for example, as 21178404 + 125316 = 4602^2 + 354^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21303693 and 21303702.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 361051 + ... + 361109.

Almost surely, 2^21303720 is an apocalyptic number.

21303720 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 21303720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37286730).

21303720 is an abundant number, since it is smaller than the sum of its proper divisors (53269740).

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

21303720 is a wasteful number, since it uses less digits than its factorization.

21303720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152 (or 86 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 18.

The square root of 21303720 is about 4615.5953028835. The cubic root of 21303720 is about 277.2161206994.

The spelling of 21303720 in words is "twenty-one million, three hundred three thousand, seven hundred twenty".