1644130261 has 4 divisors (see below), whose sum is σ = 1688566252. Its totient is φ = 1599694272.

The previous prime is 1644130259. The next prime is 1644130277. The reversal of 1644130261 is 1620314461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1507380625 + 136749636 = 38825^2 + 11694^2 .

It is a cyclic number.

It is not a de Polignac number, because 1644130261 - 2¹ = 1644130259 is a prime.

It is a super-3 number, since 3×1644130261³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644130361) 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, 22217940 + ... + 22218013.

It is an arithmetic number, because the mean of its divisors is an integer number (422141563).

Almost surely, 2^1644130261 is an apocalyptic number.

It is an amenable number.

1644130261 is a deficient number, since it is larger than the sum of its proper divisors (44435991).

1644130261 is an equidigital number, since it uses as much as digits as its factorization.

1644130261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44435990.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 1644130261 is about 40547.8761589309. The cubic root of 1644130261 is about 1180.2628594238.

It can be divided in two parts, 1644130 and 261, that added together give a triangular number (1644391 = T₁₈₁₃).

The spelling of 1644130261 in words is "one billion, six hundred forty-four million, one hundred thirty thousand, two hundred sixty-one".