21739872 has 192 divisors, whose sum is σ = 75769344. Its totient is φ = 5283840.

The previous prime is 21739859. The next prime is 21739873. The reversal of 21739872 is 27893712.

It is a self number, because there is not a number n which added to its sum of digits gives 21739872.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21739873) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 125578 + ... + 125750.

It is an arithmetic number, because the mean of its divisors is an integer number (394632).

Almost surely, 2^21739872 is an apocalyptic number.

21739872 is a gapful number since it is divisible by the number (22) 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 21739872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37884672).

21739872 is an abundant number, since it is smaller than the sum of its proper divisors (54029472).

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

21739872 is a wasteful number, since it uses less digits than its factorization.

21739872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221 (or 213 counting only the distinct ones).

The product of its digits is 42336, while the sum is 39.

The square root of 21739872 is about 4662.6035645334. The cubic root of 21739872 is about 279.0951744259.

It can be divided in two parts, 217398 and 72, that added together give a triangular number (217470 = T₆₅₉).

The spelling of 21739872 in words is "twenty-one million, seven hundred thirty-nine thousand, eight hundred seventy-two".