21606729 has 16 divisors (see below), whose sum is σ = 30170112. Its totient is φ = 13728528.

The previous prime is 21606727. The next prime is 21606731. The reversal of 21606729 is 92760612.

It is an interprime number because it is at equal distance from previous prime (21606727) and next prime (21606731).

It is not a de Polignac number, because 21606729 - 2¹ = 21606727 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21606729.

It is not an unprimeable number, because it can be changed into a prime (21606727) 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, 33282 + ... + 33924.

It is an arithmetic number, because the mean of its divisors is an integer number (1885632).

Almost surely, 2^21606729 is an apocalyptic number.

It is an amenable number.

21606729 is a deficient number, since it is larger than the sum of its proper divisors (8563383).

21606729 is a wasteful number, since it uses less digits than its factorization.

21606729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1156.

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

The square root of 21606729 is about 4648.3038842141. The cubic root of 21606729 is about 278.5242466913.

The spelling of 21606729 in words is "twenty-one million, six hundred six thousand, seven hundred twenty-nine".