21776720 has 80 divisors (see below), whose sum is σ = 59484288. Its totient is φ = 7257600.

The previous prime is 21776719. The next prime is 21776731. The reversal of 21776720 is 2767712.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20195 + ... + 21245.

Almost surely, 2^21776720 is an apocalyptic number.

21776720 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 21776720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29742144).

21776720 is an abundant number, since it is smaller than the sum of its proper divisors (37707568).

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

21776720 is a wasteful number, since it uses less digits than its factorization.

21776720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1108 (or 1102 counting only the distinct ones).

The product of its (nonzero) digits is 8232, while the sum is 32.

The square root of 21776720 is about 4666.5533319571. The cubic root of 21776720 is about 279.2527695596.

The spelling of 21776720 in words is "twenty-one million, seven hundred seventy-six thousand, seven hundred twenty".