21606740 has 24 divisors (see below), whose sum is σ = 46940040. Its totient is φ = 8344448.

The previous prime is 21606733. The next prime is 21606751. The reversal of 21606740 is 4760612.

It can be written as a sum of positive squares in 4 ways, for example, as 9314704 + 12292036 = 3052^2 + 3506^2 .

It is a congruent number.

It is an unprimeable number.

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, 18047 + ... + 19206.

It is an arithmetic number, because the mean of its divisors is an integer number (1955835).

Almost surely, 2^21606740 is an apocalyptic number.

21606740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21606740 is an abundant number, since it is smaller than the sum of its proper divisors (25333300).

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

21606740 is a wasteful number, since it uses less digits than its factorization.

21606740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37291 (or 37289 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 21606740 is about 4648.3050674412. The cubic root of 21606740 is about 278.5242939569.

The spelling of 21606740 in words is "twenty-one million, six hundred six thousand, seven hundred forty".