261972180 has 72 divisors (see below), whose sum is σ = 805574952. Its totient is φ = 68898816.

The previous prime is 261972127. The next prime is 261972181. The reversal of 261972180 is 81279162.

It can be written as a sum of positive squares in 4 ways, for example, as 8398404 + 253573776 = 2898^2 + 15924^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261972181) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3172 + ... + 23108.

It is an arithmetic number, because the mean of its divisors is an integer number (11188541).

Almost surely, 2^261972180 is an apocalyptic number.

261972180 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 261972180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (402787476).

261972180 is an abundant number, since it is smaller than the sum of its proper divisors (543602772).

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

261972180 is a wasteful number, since it uses less digits than its factorization.

261972180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20025 (or 20020 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The square root of 261972180 is about 16185.5546707550. The cubic root of 261972180 is about 639.8601419653.

The spelling of 261972180 in words is "two hundred sixty-one million, nine hundred seventy-two thousand, one hundred eighty".