21729144390 has 16 divisors (see below), whose sum is σ = 52149946608. Its totient is φ = 5794438496.

The previous prime is 21729144373. The next prime is 21729144391. The reversal of 21729144390 is 9344192712.

It is a happy number.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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 (21729144391) 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, 362152377 + ... + 362152436.

It is an arithmetic number, because the mean of its divisors is an integer number (3259371663).

Almost surely, 2^21729144390 is an apocalyptic number.

21729144390 is an abundant number, since it is smaller than the sum of its proper divisors (30420802218).

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

21729144390 is a wasteful number, since it uses less digits than its factorization.

21729144390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724304823.

The product of its (nonzero) digits is 108864, while the sum is 42.

The spelling of 21729144390 in words is "twenty-one billion, seven hundred twenty-nine million, one hundred forty-four thousand, three hundred ninety".