21725816 has 48 divisors (see below), whose sum is σ = 49897800. Its totient is φ = 8817984.

The previous prime is 21725801. The next prime is 21725819. The reversal of 21725816 is 61852712.

It is a super-2 number, since 2×21725816² = 944022161731712, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21725819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5990 + ... + 8906.

Almost surely, 2^21725816 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 21725816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24948900).

21725816 is an abundant number, since it is smaller than the sum of its proper divisors (28171984).

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

21725816 is a wasteful number, since it uses less digits than its factorization.

21725816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2956 (or 2945 counting only the distinct ones).

The product of its digits is 6720, while the sum is 32.

The square root of 21725816 is about 4661.0960084512. The cubic root of 21725816 is about 279.0350114291.

The spelling of 21725816 in words is "twenty-one million, seven hundred twenty-five thousand, eight hundred sixteen".