21739648 has 64 divisors (see below), whose sum is σ = 52142400. Its totient is φ = 8819712.

The previous prime is 21739643. The next prime is 21739661. The reversal of 21739648 is 84693712.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21739648² = 945224590327808, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21739648.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21739643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16386 + ... + 17662.

It is an arithmetic number, because the mean of its divisors is an integer number (814725).

Almost surely, 2^21739648 is an apocalyptic number.

21739648 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21739648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26071200).

21739648 is an abundant number, since it is smaller than the sum of its proper divisors (30402752).

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

21739648 is a wasteful number, since it uses less digits than its factorization.

21739648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1317 (or 1305 counting only the distinct ones).

The product of its digits is 72576, while the sum is 40.

The square root of 21739648 is about 4662.5795435574. The cubic root of 21739648 is about 279.0942158564.

The spelling of 21739648 in words is "twenty-one million, seven hundred thirty-nine thousand, six hundred forty-eight".