21759640 has 32 divisors (see below), whose sum is σ = 55954080. Its totient is φ = 7460352.

The previous prime is 21759631. The next prime is 21759653. The reversal of 21759640 is 4695712.

It is a junction number, because it is equal to n+sod(n) for n = 21759596 and 21759605.

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, 38577 + ... + 39136.

It is an arithmetic number, because the mean of its divisors is an integer number (1748565).

Almost surely, 2^21759640 is an apocalyptic number.

21759640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21759640 is an abundant number, since it is smaller than the sum of its proper divisors (34194440).

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

21759640 is a wasteful number, since it uses less digits than its factorization.

21759640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77731 (or 77727 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21759640 is about 4664.7229285350. The cubic root of 21759640 is about 279.1797422652.

The spelling of 21759640 in words is "twenty-one million, seven hundred fifty-nine thousand, six hundred forty".