21767840 has 48 divisors (see below), whose sum is σ = 52830792. Its totient is φ = 8469504.

The previous prime is 21767839. The next prime is 21767869. The reversal of 21767840 is 4876712.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 21641104 + 126736 = 4652^2 + 356^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21767840.

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, 4082 + ... + 7758.

Almost surely, 2^21767840 is an apocalyptic number.

21767840 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 21767840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26415396).

21767840 is an abundant number, since it is smaller than the sum of its proper divisors (31062952).

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

21767840 is a wasteful number, since it uses less digits than its factorization.

21767840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3729 (or 3721 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 35.

The square root of 21767840 is about 4665.6017832644. The cubic root of 21767840 is about 279.2148069749.

The spelling of 21767840 in words is "twenty-one million, seven hundred sixty-seven thousand, eight hundred forty".