21299616 has 72 divisors (see below), whose sum is σ = 65241540. Its totient is φ = 6552576.

The previous prime is 21299611. The next prime is 21299639. The reversal of 21299616 is 61699212.

It can be written as a sum of positive squares in 2 ways, for example, as 21123216 + 176400 = 4596^2 + 420^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21299611) 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 11 ways as a sum of consecutive naturals, for example, 900 + ... + 6588.

Almost surely, 2^21299616 is an apocalyptic number.

21299616 is a gapful number since it is divisible by the number (26) 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 21299616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32620770).

21299616 is an abundant number, since it is smaller than the sum of its proper divisors (43941924).

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

21299616 is a wasteful number, since it uses less digits than its factorization.

21299616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5718 (or 5707 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 21299616 is about 4615.1507017648. The cubic root of 21299616 is about 277.1983183621.

The spelling of 21299616 in words is "twenty-one million, two hundred ninety-nine thousand, six hundred sixteen".