21640696 has 96 divisors (see below), whose sum is σ = 54518400. Its totient is φ = 7801920.

The previous prime is 21640693. The next prime is 21640721. The reversal of 21640696 is 69604612.

21640696 = T₂₆₃ + T₂₆₄ + ... + T₅₂₈.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 503251 + ... + 503293.

It is an arithmetic number, because the mean of its divisors is an integer number (567900).

Almost surely, 2^21640696 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21640696, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27259200).

21640696 is an abundant number, since it is smaller than the sum of its proper divisors (32877704).

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

21640696 is a wasteful number, since it uses less digits than its factorization.

21640696 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129 (or 82 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 34.

The square root of 21640696 is about 4651.9561476867. The cubic root of 21640696 is about 278.6701222325.

The spelling of 21640696 in words is "twenty-one million, six hundred forty thousand, six hundred ninety-six".