21761440 has 48 divisors (see below), whose sum is σ = 52623648. Its totient is φ = 8499456.

The previous prime is 21761437. The next prime is 21761459. The reversal of 21761440 is 4416712.

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, 5299 + ... + 8461.

It is an arithmetic number, because the mean of its divisors is an integer number (1096326).

Almost surely, 2^21761440 is an apocalyptic number.

21761440 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 21761440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26311824).

21761440 is an abundant number, since it is smaller than the sum of its proper divisors (30862208).

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

21761440 is a wasteful number, since it uses less digits than its factorization.

21761440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3221 (or 3213 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21761440 is about 4664.9158620494. The cubic root of 21761440 is about 279.1874401511.

It can be divided in two parts, 21761 and 440, that added together give a square (22201 = 149²).

The spelling of 21761440 in words is "twenty-one million, seven hundred sixty-one thousand, four hundred forty".