21729660 has 24 divisors (see below), whose sum is σ = 60843216. Its totient is φ = 5794560.

The previous prime is 21729647. The next prime is 21729683. The reversal of 21729660 is 6692712.

It is a super-3 number, since 3×21729660³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 181021 + ... + 181140.

It is an arithmetic number, because the mean of its divisors is an integer number (2535134).

Almost surely, 2^21729660 is an apocalyptic number.

21729660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21729660 is an abundant number, since it is smaller than the sum of its proper divisors (39113556).

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

21729660 is a wasteful number, since it uses less digits than its factorization.

21729660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 362173 (or 362171 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 21729660 is about 4661.5083395828. The cubic root of 21729660 is about 279.0514672334.

The spelling of 21729660 in words is "twenty-one million, seven hundred twenty-nine thousand, six hundred sixty".