21329644 has 12 divisors (see below), whose sum is σ = 42659344. Its totient is φ = 9141264.

The previous prime is 21329641. The next prime is 21329663. The reversal of 21329644 is 44692312.

It is a happy number.

21329644 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21329641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 380859 + ... + 380914.

Almost surely, 2^21329644 is an apocalyptic number.

It is an amenable number.

21329644 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21329644 is a wasteful number, since it uses less digits than its factorization.

21329644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 761784 (or 761782 counting only the distinct ones).

The product of its digits is 10368, while the sum is 31.

The square root of 21329644 is about 4618.4027541998. The cubic root of 21329644 is about 277.3285210632.

The spelling of 21329644 in words is "twenty-one million, three hundred twenty-nine thousand, six hundred forty-four".