21720496 has 80 divisors (see below), whose sum is σ = 51782400. Its totient is φ = 8619264.

The previous prime is 21720481. The next prime is 21720499. The reversal of 21720496 is 69402712.

It is not an unprimeable number, because it can be changed into a prime (21720499) 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 15 ways as a sum of consecutive naturals, for example, 125466 + ... + 125638.

It is an arithmetic number, because the mean of its divisors is an integer number (647280).

Almost surely, 2^21720496 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 21720496, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25891200).

21720496 is an abundant number, since it is smaller than the sum of its proper divisors (30061904).

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

21720496 is a wasteful number, since it uses less digits than its factorization.

21720496 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 266 (or 260 counting only the distinct ones).

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

The square root of 21720496 is about 4660.5252922820. The cubic root of 21720496 is about 279.0122338045.

The spelling of 21720496 in words is "twenty-one million, seven hundred twenty thousand, four hundred ninety-six".