21729365 has 16 divisors (see below), whose sum is σ = 31097088. Its totient is φ = 14251776.

The previous prime is 21729361. The next prime is 21729377. The reversal of 21729365 is 56392712.

It is not a de Polignac number, because 21729365 - 2² = 21729361 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21729361) 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 15 ways as a sum of consecutive naturals, for example, 12692 + ... + 14301.

It is an arithmetic number, because the mean of its divisors is an integer number (1943568).

Almost surely, 2^21729365 is an apocalyptic number.

It is an amenable number.

21729365 is a deficient number, since it is larger than the sum of its proper divisors (9367723).

21729365 is a wasteful number, since it uses less digits than its factorization.

21729365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27028.

The product of its digits is 22680, while the sum is 35.

The square root of 21729365 is about 4661.4766973568. The cubic root of 21729365 is about 279.0502044348.

The spelling of 21729365 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred sixty-five".