261445640 has 16 divisors (see below), whose sum is σ = 588252780. Its totient is φ = 104578240.

The previous prime is 261445627. The next prime is 261445649. The reversal of 261445640 is 46544162.

It can be written as a sum of positive squares in 2 ways, for example, as 241926916 + 19518724 = 15554^2 + 4418^2 .

It is a junction number, because it is equal to n+sod(n) for n = 261445597 and 261445606.

It is not an unprimeable number, because it can be changed into a prime (261445649) 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, 3268031 + ... + 3268110.

Almost surely, 2^261445640 is an apocalyptic number.

261445640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261445640 is an abundant number, since it is smaller than the sum of its proper divisors (326807140).

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

261445640 is a wasteful number, since it uses less digits than its factorization.

261445640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6536152 (or 6536148 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 32.

The square root of 261445640 is about 16169.2807508559. The cubic root of 261445640 is about 639.4311677485.

The spelling of 261445640 in words is "two hundred sixty-one million, four hundred forty-five thousand, six hundred forty".