21150720 has 264 divisors, whose sum is σ = 80471664. Its totient is φ = 5308416.

The previous prime is 21150719. The next prime is 21150739. The reversal of 21150720 is 2705112.

It is a hoax number, since the sum of its digits (18) coincides with the sum of the digits of its distinct prime factors.

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

It is a nialpdrome in base 12.

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 21150693 and 21150702.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1244152 + ... + 1244168.

Almost surely, 2^21150720 is an apocalyptic number.

21150720 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 21150720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40235832).

21150720 is an abundant number, since it is smaller than the sum of its proper divisors (59320944).

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

21150720 is an equidigital number, since it uses as much as digits as its factorization.

21150720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57 (or 27 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21150720 is about 4598.9911937293. The cubic root of 21150720 is about 276.5508846027.

Adding to 21150720 its reverse (2705112), we get a palindrome (23855832).

The spelling of 21150720 in words is "twenty-one million, one hundred fifty thousand, seven hundred twenty".