21319816 has 32 divisors (see below), whose sum is σ = 47162880. Its totient is φ = 8841600.

The previous prime is 21319813. The next prime is 21319817. The reversal of 21319816 is 61891312.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21319813) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4405 + ... + 7876.

It is an arithmetic number, because the mean of its divisors is an integer number (1473840).

Almost surely, 2^21319816 is an apocalyptic number.

It is an amenable number.

21319816 is an abundant number, since it is smaller than the sum of its proper divisors (25843064).

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

21319816 is a wasteful number, since it uses less digits than its factorization.

21319816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12325 (or 12321 counting only the distinct ones).

The product of its digits is 2592, while the sum is 31.

The square root of 21319816 is about 4617.3386273913. The cubic root of 21319816 is about 277.2859198922.

The spelling of 21319816 in words is "twenty-one million, three hundred nineteen thousand, eight hundred sixteen".