21697440 has 96 divisors (see below), whose sum is σ = 72394560. Its totient is φ = 5443584.

The previous prime is 21697439. The next prime is 21697451. The reversal of 21697440 is 4479612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6831 + ... + 9489.

It is an arithmetic number, because the mean of its divisors is an integer number (754110).

Almost surely, 2^21697440 is an apocalyptic number.

21697440 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 21697440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36197280).

21697440 is an abundant number, since it is smaller than the sum of its proper divisors (50697120).

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

21697440 is a wasteful number, since it uses less digits than its factorization.

21697440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2694 (or 2686 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 21697440 is about 4658.0510946103. The cubic root of 21697440 is about 278.9134763367.

The spelling of 21697440 in words is "twenty-one million, six hundred ninety-seven thousand, four hundred forty".