21173772 has 48 divisors (see below), whose sum is σ = 52641792. Its totient is φ = 6600960.

The previous prime is 21173767. The next prime is 21173773. The reversal of 21173772 is 27737112.

It is not an unprimeable number, because it can be changed into a prime (21173773) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55093 + ... + 55475.

It is an arithmetic number, because the mean of its divisors is an integer number (1096704).

Almost surely, 2^21173772 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 21173772, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26320896).

21173772 is an abundant number, since it is smaller than the sum of its proper divisors (31468020).

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

21173772 is a wasteful number, since it uses less digits than its factorization.

21173772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 678 (or 676 counting only the distinct ones).

The product of its digits is 4116, while the sum is 30.

The square root of 21173772 is about 4601.4967130272. The cubic root of 21173772 is about 276.6513183208.

It can be divided in two parts, 21173 and 772, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21173772 in words is "twenty-one million, one hundred seventy-three thousand, seven hundred seventy-two".