1001155661 has 16 divisors (see below), whose sum is σ = 1178962560. Its totient is φ = 840544320.

The previous prime is 1001155651. The next prime is 1001155669. The reversal of 1001155661 is 1665511001.

It is a de Polignac number, because none of the positive numbers 2^k-1001155661 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1001155661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1001155669) 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 15 ways as a sum of consecutive naturals, for example, 60890 + ... + 75563.

It is an arithmetic number, because the mean of its divisors is an integer number (73685160).

Almost surely, 2^1001155661 is an apocalyptic number.

1001155661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1001155661 is a deficient number, since it is larger than the sum of its proper divisors (177806899).

1001155661 is a wasteful number, since it uses less digits than its factorization.

1001155661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136516.

The product of its (nonzero) digits is 900, while the sum is 26.

The square root of 1001155661 is about 31641.0439303130. The cubic root of 1001155661 is about 1000.3850720338.

Adding to 1001155661 its reverse (1665511001), we get a palindrome (2666666662).

The spelling of 1001155661 in words is "one billion, one million, one hundred fifty-five thousand, six hundred sixty-one".