21694720 has 72 divisors (see below), whose sum is σ = 55077624. Its totient is φ = 8159232.

The previous prime is 21694709. The next prime is 21694721. The reversal of 21694720 is 2749612.

It can be written as a sum of positive squares in 4 ways, for example, as 8386816 + 13307904 = 2896^2 + 3648^2 .

It is not an unprimeable number, because it can be changed into a prime (21694721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21262 + ... + 22258.

It is an arithmetic number, because the mean of its divisors is an integer number (764967).

Almost surely, 2^21694720 is an apocalyptic number.

21694720 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 21694720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27538812).

21694720 is an abundant number, since it is smaller than the sum of its proper divisors (33382904).

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

21694720 is an equidigital number, since it uses as much as digits as its factorization.

21694720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1035 (or 1021 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 31.

The square root of 21694720 is about 4657.7591178591. The cubic root of 21694720 is about 278.9018209470.

It can be divided in two parts, 2169 and 4720, that added together give a square (6889 = 83²).

The spelling of 21694720 in words is "twenty-one million, six hundred ninety-four thousand, seven hundred twenty".