21049644 has 144 divisors (see below), whose sum is σ = 65542400. Its totient is φ = 5132160.

The previous prime is 21049643. The next prime is 21049667. The reversal of 21049644 is 44694012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21049643) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 193062 + ... + 193170.

Almost surely, 2^21049644 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21049644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32771200).

21049644 is an abundant number, since it is smaller than the sum of its proper divisors (44492756).

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

21049644 is a wasteful number, since it uses less digits than its factorization.

21049644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164 (or 151 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21049644 is about 4587.9891019923. The cubic root of 21049644 is about 276.1096497741.

The spelling of 21049644 in words is "twenty-one million, forty-nine thousand, six hundred forty-four".