261678605 has 8 divisors (see below), whose sum is σ = 321673464. Its totient is φ = 204236800.

The previous prime is 261678581. The next prime is 261678619. The reversal of 261678605 is 506876162.

It can be written as a sum of positive squares in 4 ways, for example, as 1630729 + 260047876 = 1277^2 + 16126^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261678605 - 2¹⁶ = 261613069 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 638036 + ... + 638445.

It is an arithmetic number, because the mean of its divisors is an integer number (40209183).

Almost surely, 2^261678605 is an apocalyptic number.

It is an amenable number.

261678605 is a deficient number, since it is larger than the sum of its proper divisors (59994859).

261678605 is a wasteful number, since it uses less digits than its factorization.

261678605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1276527.

The product of its (nonzero) digits is 120960, while the sum is 41.

The square root of 261678605 is about 16176.4830850219. The cubic root of 261678605 is about 639.6210362276.

The spelling of 261678605 in words is "two hundred sixty-one million, six hundred seventy-eight thousand, six hundred five".