21723396 has 12 divisors (see below), whose sum is σ = 50687952. Its totient is φ = 7241128.

The previous prime is 21723389. The next prime is 21723397. The reversal of 21723396 is 69332712.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21723397) 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 3 ways as a sum of consecutive naturals, for example, 905130 + ... + 905153.

It is an arithmetic number, because the mean of its divisors is an integer number (4223996).

Almost surely, 2^21723396 is an apocalyptic number.

It is an amenable number.

21723396 is an abundant number, since it is smaller than the sum of its proper divisors (28964556).

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

21723396 is a wasteful number, since it uses less digits than its factorization.

21723396 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1810290 (or 1810288 counting only the distinct ones).

The product of its digits is 13608, while the sum is 33.

The square root of 21723396 is about 4660.8364056251. The cubic root of 21723396 is about 279.0246506399.

The spelling of 21723396 in words is "twenty-one million, seven hundred twenty-three thousand, three hundred ninety-six".