210661440 has 112 divisors (see below), whose sum is σ = 729691200. Its totient is φ = 51066880.

The previous prime is 210661427. The next prime is 210661441. The reversal of 210661440 is 44166012.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 210661440.

It is not an unprimeable number, because it can be changed into a prime (210661441) 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, 586 + ... + 20534.

It is an arithmetic number, because the mean of its divisors is an integer number (6515100).

Almost surely, 2^210661440 is an apocalyptic number.

210661440 is a gapful number since it is divisible by the number (20) 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 210661440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (364845600).

210661440 is an abundant number, since it is smaller than the sum of its proper divisors (519029760).

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

210661440 is a wasteful number, since it uses less digits than its factorization.

210661440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19980 (or 19970 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 210661440 is about 14514.1806520382. The cubic root of 210661440 is about 595.0155964181.

It can be divided in two parts, 2106 and 61440, that added together give a triangular number (63546 = T₃₅₆).

The spelling of 210661440 in words is "two hundred ten million, six hundred sixty-one thousand, four hundred forty".