261331620 has 96 divisors (see below), whose sum is σ = 803367936. Its totient is φ = 62947200.

The previous prime is 261331619. The next prime is 261331627. The reversal of 261331620 is 26133162.

It is a happy number.

It is a super-2 number, since 2×261331620² = 136588431223648800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261331627) 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, 109035 + ... + 111405.

It is an arithmetic number, because the mean of its divisors is an integer number (8368416).

Almost surely, 2^261331620 is an apocalyptic number.

261331620 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 261331620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (401683968).

261331620 is an abundant number, since it is smaller than the sum of its proper divisors (542036316).

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

261331620 is a wasteful number, since it uses less digits than its factorization.

261331620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2561 (or 2559 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 24.

The square root of 261331620 is about 16165.7545447158. The cubic root of 261331620 is about 639.3381993555.

Adding to 261331620 its reverse (26133162), we get a palindrome (287464782).

The spelling of 261331620 in words is "two hundred sixty-one million, three hundred thirty-one thousand, six hundred twenty".