261391940 has 12 divisors (see below), whose sum is σ = 548923116. Its totient is φ = 104556768.

The previous prime is 261391937. The next prime is 261391943. The reversal of 261391940 is 49193162.

It is an interprime number because it is at equal distance from previous prime (261391937) and next prime (261391943).

It can be written as a sum of positive squares in 2 ways, for example, as 198697216 + 62694724 = 14096^2 + 7918^2 .

It is a super-3 number, since 3×261391940³ (a number of 26 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 261391940.

It is not an unprimeable number, because it can be changed into a prime (261391943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6534779 + ... + 6534818.

It is an arithmetic number, because the mean of its divisors is an integer number (45743593).

Almost surely, 2^261391940 is an apocalyptic number.

261391940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261391940 is an abundant number, since it is smaller than the sum of its proper divisors (287531176).

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

261391940 is a wasteful number, since it uses less digits than its factorization.

261391940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13069606 (or 13069604 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 261391940 is about 16167.6201093420. The cubic root of 261391940 is about 639.3873857920.

The spelling of 261391940 in words is "two hundred sixty-one million, three hundred ninety-one thousand, nine hundred forty".