21531760 has 40 divisors (see below), whose sum is σ = 50371776. Its totient is φ = 8559360.

The previous prime is 21531739. The next prime is 21531773. The reversal of 21531760 is 6713512.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13737 + ... + 15223.

Almost surely, 2^21531760 is an apocalyptic number.

21531760 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 21531760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25185888).

21531760 is an abundant number, since it is smaller than the sum of its proper divisors (28840016).

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

21531760 is a wasteful number, since it uses less digits than its factorization.

21531760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1681 (or 1675 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21531760 is about 4640.2327527830. The cubic root of 21531760 is about 278.2017409747.

The spelling of 21531760 in words is "twenty-one million, five hundred thirty-one thousand, seven hundred sixty".