61809865 has 8 divisors (see below), whose sum is σ = 79877448. Its totient is φ = 45644160.

The previous prime is 61809863. The next prime is 61809889. The reversal of 61809865 is 56890816.

It can be written as a sum of positive squares in 4 ways, for example, as 1530169 + 60279696 = 1237^2 + 7764^2 .

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

It is not a de Polignac number, because 61809865 - 2¹ = 61809863 is a prime.

It is a super-5 number, since 5×61809865⁵ (a number of 40 digits) contains 55555 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61809863) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 475396 + ... + 475525.

It is an arithmetic number, because the mean of its divisors is an integer number (9984681).

Almost surely, 2^61809865 is an apocalyptic number.

61809865 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

61809865 is a deficient number, since it is larger than the sum of its proper divisors (18067583).

61809865 is a wasteful number, since it uses less digits than its factorization.

61809865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 950939.

The product of its (nonzero) digits is 103680, while the sum is 43.

The square root of 61809865 is about 7861.9250187216. The cubic root of 61809865 is about 395.3841586573.

The spelling of 61809865 in words is "sixty-one million, eight hundred nine thousand, eight hundred sixty-five".