61005781 has 4 divisors (see below), whose sum is σ = 61027564. Its totient is φ = 60984000.

The previous prime is 61005779. The next prime is 61005787. The reversal of 61005781 is 18750016.

It is a happy number.

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 37638225 + 23367556 = 6135^2 + 4834^2 .

It is a cyclic number.

It is not a de Polignac number, because 61005781 - 2¹ = 61005779 is a prime.

It is a super-2 number, since 2×61005781² = 7443410630839922, which contains 22 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 (61005787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5940 + ... + 12541.

It is an arithmetic number, because the mean of its divisors is an integer number (15256891).

Almost surely, 2^61005781 is an apocalyptic number.

It is an amenable number.

61005781 is a deficient number, since it is larger than the sum of its proper divisors (21783).

61005781 is a wasteful number, since it uses less digits than its factorization.

61005781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21782.

The product of its (nonzero) digits is 1680, while the sum is 28.

The square root of 61005781 is about 7810.6197577401. The cubic root of 61005781 is about 393.6621533765.

Adding to 61005781 its reverse (18750016), we get a palindrome (79755797).

It can be divided in two parts, 6100 and 5781, that added together give a square (11881 = 109²).

The spelling of 61005781 in words is "sixty-one million, five thousand, seven hundred eighty-one".