1261638 has 96 divisors (see below), whose sum is σ = 3594240. Its totient is φ = 311040.

The previous prime is 1261627. The next prime is 1261639. The reversal of 1261638 is 8361621.

1261638 is a `hidden beast` number, since 1 + 26 + 1 + 638 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 40683 + ... + 40713.

It is an arithmetic number, because the mean of its divisors is an integer number (37440).

2^1261638 is an apocalyptic number.

1261638 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1261638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1797120).

1261638 is an abundant number, since it is smaller than the sum of its proper divisors (2332602).

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

1261638 is a wasteful number, since it uses less digits than its factorization.

1261638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82 (or 79 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 1261638 is about 1123.2266022491. The cubic root of 1261638 is about 108.0550131249.

It can be divided in two parts, 126 and 1638, that added together give a square (1764 = 42²).

The spelling of 1261638 in words is "one million, two hundred sixty-one thousand, six hundred thirty-eight".