61581581 has 2 divisors, whose sum is σ = 61581582. Its totient is φ = 61581580.

The previous prime is 61581577. The next prime is 61581589. The reversal of 61581581 is 18518516.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 32959081 + 28622500 = 5741^2 + 5350^2 .

It is a cyclic number.

It is not a de Polignac number, because 61581581 - 2² = 61581577 is a prime.

It is a super-2 number, since 2×61581581² = 7584582236919122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61581589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30790790 + 30790791.

It is an arithmetic number, because the mean of its divisors is an integer number (30790791).

Almost surely, 2^61581581 is an apocalyptic number.

It is an amenable number.

61581581 is a deficient number, since it is larger than the sum of its proper divisors (1).

61581581 is an equidigital number, since it uses as much as digits as its factorization.

61581581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9600, while the sum is 35.

The square root of 61581581 is about 7847.3932614595. The cubic root of 61581581 is about 394.8967972652.

The spelling of 61581581 in words is "sixty-one million, five hundred eighty-one thousand, five hundred eighty-one".