21577920 has 336 divisors, whose sum is σ = 89245440. Its totient is φ = 4313088.

The previous prime is 21577877. The next prime is 21577921. The reversal of 21577920 is 2977512.

It is a tau number, because it is divible by the number of its divisors (336).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21577921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1135671 + ... + 1135689.

Almost surely, 2^21577920 is an apocalyptic number.

21577920 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 21577920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44622720).

21577920 is an abundant number, since it is smaller than the sum of its proper divisors (67667520).

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

21577920 is a wasteful number, since it uses less digits than its factorization.

21577920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72 (or 49 counting only the distinct ones).

The product of its (nonzero) digits is 8820, while the sum is 33.

The square root of 21577920 is about 4645.2039782985. The cubic root of 21577920 is about 278.4004029589.

The spelling of 21577920 in words is "twenty-one million, five hundred seventy-seven thousand, nine hundred twenty".