21917680 has 20 divisors (see below), whose sum is σ = 50958792. Its totient is φ = 8767040.

The previous prime is 21917677. The next prime is 21917683. The reversal of 21917680 is 8671912.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21917677) and next prime (21917683).

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136906 + ... + 137065.

Almost surely, 2^21917680 is an apocalyptic number.

21917680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21917680 is an abundant number, since it is smaller than the sum of its proper divisors (29041112).

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

21917680 is a wasteful number, since it uses less digits than its factorization.

21917680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273984 (or 273978 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 21917680 is about 4681.6321940110. The cubic root of 21917680 is about 279.8540055231.

The spelling of 21917680 in words is "twenty-one million, nine hundred seventeen thousand, six hundred eighty".