21729370 has 16 divisors (see below), whose sum is σ = 42121800. Its totient is φ = 8023104.

The previous prime is 21729361. The next prime is 21729377. The reversal of 21729370 is 7392712.

It can be written as a sum of positive squares in 4 ways, for example, as 6589489 + 15139881 = 2567^2 + 3891^2 .

It is not an unprimeable number, because it can be changed into a prime (21729377) 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, 83445 + ... + 83704.

Almost surely, 2^21729370 is an apocalyptic number.

21729370 is a deficient number, since it is larger than the sum of its proper divisors (20392430).

21729370 is a wasteful number, since it uses less digits than its factorization.

21729370 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167169.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 21729370 is about 4661.4772336675. The cubic root of 21729370 is about 279.0502258383.

The spelling of 21729370 in words is "twenty-one million, seven hundred twenty-nine thousand, three hundred seventy".