21767940 has 84 divisors (see below), whose sum is σ = 68583564. Its totient is φ = 5800896.

The previous prime is 21767929. The next prime is 21767947. The reversal of 21767940 is 4976712.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13883076 + 7884864 = 3726^2 + 2808^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21767895 and 21767904.

It is not an unprimeable number, because it can be changed into a prime (21767947) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 13834 + ... + 15326.

It is an arithmetic number, because the mean of its divisors is an integer number (816471).

Almost surely, 2^21767940 is an apocalyptic number.

21767940 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 21767940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34291782).

21767940 is an abundant number, since it is smaller than the sum of its proper divisors (46815624).

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

21767940 is a wasteful number, since it uses less digits than its factorization.

21767940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1520 (or 1503 counting only the distinct ones).

The product of its (nonzero) digits is 21168, while the sum is 36.

The square root of 21767940 is about 4665.6124999833. The cubic root of 21767940 is about 279.2152345390.

The spelling of 21767940 in words is "twenty-one million, seven hundred sixty-seven thousand, nine hundred forty".