261638 has 16 divisors (see below), whose sum is σ = 438480. Its totient is φ = 116256.
The previous prime is 261637. The next prime is 261641. The reversal of 261638 is 836162.
It is a Harshad number since it is a multiple of its sum of digits (26).
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (261631) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (11) of ones.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 581 + ... + 927.
It is an arithmetic number, because the mean of its divisors is an integer number (27405).
2261638 is an apocalyptic number.
261638 is a deficient number, since it is larger than the sum of its proper divisors (176842).
261638 is a wasteful number, since it uses less digits than its factorization.
261638 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 391.
The product of its digits is 1728, while the sum is 26.
The square root of 261638 is about 511.5056206925. The cubic root of 261638 is about 63.9587950915.
The spelling of 261638 in words is "two hundred sixty-one thousand, six hundred thirty-eight".
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