21701680 has 160 divisors (see below), whose sum is σ = 67995648. Its totient is φ = 6220800.

The previous prime is 21701651. The next prime is 21701683. The reversal of 21701680 is 8610712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21701683) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 79945 + ... + 80215.

Almost surely, 2^21701680 is an apocalyptic number.

21701680 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 21701680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33997824).

21701680 is an abundant number, since it is smaller than the sum of its proper divisors (46293968).

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

21701680 is a wasteful number, since it uses less digits than its factorization.

21701680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 315 (or 309 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 21701680 is about 4658.5061983430. The cubic root of 21701680 is about 278.9316430900.

The spelling of 21701680 in words is "twenty-one million, seven hundred one thousand, six hundred eighty".