61581896649 has 189 divisors, whose sum is σ = 117465358149. Its totient is φ = 32161147200.

The previous prime is 61581896611. The next prime is 61581896689. The reversal of 61581896649 is 94669818516.

The square root of 61581896649 is 248157.

It is a perfect power (a square), and thus also a powerful number.

61581896649 is a `hidden beast` number, since 6 + 1 + 581 + 8 + 9 + 6 + 6 + 49 = 666.

61581896649 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 2322758025 + 59259138624 = 48195^2 + 243432^2 .

It is a tau number, because it is divible by the number of its divisors (189).

It is not a de Polignac number, because 61581896649 - 2¹³ = 61581888457 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (61581896609) by changing a digit.

It is a polite number, since it can be written in 188 ways as a sum of consecutive naturals, for example, 609721699 + ... + 609721799.

Almost surely, 2^61581896649 is an apocalyptic number.

61581896649 is the 248157-th square number.

61581896649 is the 124079-th centered octagonal number.

It is an amenable number.

61581896649 is a deficient number, since it is larger than the sum of its proper divisors (55883461500).

61581896649 is an equidigital number, since it uses as much as digits as its factorization.

61581896649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260 (or 124 counting only the distinct ones).

The product of its digits is 22394880, while the sum is 63.

The spelling of 61581896649 in words is "sixty-one billion, five hundred eighty-one million, eight hundred ninety-six thousand, six hundred forty-nine".