61781609 has 2 divisors, whose sum is σ = 61781610. Its totient is φ = 61781608.

The previous prime is 61781591. The next prime is 61781617. The reversal of 61781609 is 90618716.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61387225 + 394384 = 7835^2 + 628^2 .

It is a cyclic number.

It is not a de Polignac number, because 61781609 - 2⁸ = 61781353 is a prime.

It is not a weakly prime, because it can be changed into another prime (61784609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30890804 + 30890805.

It is an arithmetic number, because the mean of its divisors is an integer number (30890805).

Almost surely, 2^61781609 is an apocalyptic number.

It is an amenable number.

61781609 is a deficient number, since it is larger than the sum of its proper divisors (1).

61781609 is an equidigital number, since it uses as much as digits as its factorization.

61781609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 61781609 is about 7860.1277979432. The cubic root of 61781609 is about 395.3239003279.

The spelling of 61781609 in words is "sixty-one million, seven hundred eighty-one thousand, six hundred nine".