661581099 has 6 divisors (see below), whose sum is σ = 955617156. Its totient is φ = 441054060.

The previous prime is 661581097. The next prime is 661581113. The reversal of 661581099 is 990185166.

661581099 is a `hidden beast` number, since 6 + 61 + 581 + 0 + 9 + 9 = 666.

It is not a de Polignac number, because 661581099 - 2¹ = 661581097 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661581097) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36754497 + ... + 36754514.

It is an arithmetic number, because the mean of its divisors is an integer number (159269526).

Almost surely, 2^661581099 is an apocalyptic number.

661581099 is a deficient number, since it is larger than the sum of its proper divisors (294036057).

661581099 is a wasteful number, since it uses less digits than its factorization.

661581099 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73509017 (or 73509014 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 45.

The square root of 661581099 is about 25721.2188474808. The cubic root of 661581099 is about 871.3534660409.

The spelling of 661581099 in words is "six hundred sixty-one million, five hundred eighty-one thousand, ninety-nine".