21208616 has 32 divisors (see below), whose sum is σ = 46720800. Its totient is φ = 8898240.

The previous prime is 21208613. The next prime is 21208633. The reversal of 21208616 is 61680212.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is not an unprimeable number, because it can be changed into a prime (21208613) 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 7 ways as a sum of consecutive naturals, for example, 8126 + ... + 10413.

It is an arithmetic number, because the mean of its divisors is an integer number (1460025).

Almost surely, 2^21208616 is an apocalyptic number.

21208616 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21208616 is an abundant number, since it is smaller than the sum of its proper divisors (25512184).

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

21208616 is a wasteful number, since it uses less digits than its factorization.

21208616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18569 (or 18565 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 21208616 is about 4605.2813160544. The cubic root of 21208616 is about 276.8029895430.

Adding to 21208616 its reverse (61680212), we get a palindrome (82888828).

The spelling of 21208616 in words is "twenty-one million, two hundred eight thousand, six hundred sixteen".