661005099981 has 12 divisors (see below), whose sum is σ = 956698548000. Its totient is φ = 439786957320.

The previous prime is 661005099949. The next prime is 661005099983. The reversal of 661005099981 is 189990500166.

It is not a de Polignac number, because 661005099981 - 2⁵ = 661005099949 is a prime.

It is a super-2 number, since 2×661005099981² (a number of 24 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661005099983) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 73587705 + ... + 73596686.

It is an arithmetic number, because the mean of its divisors is an integer number (79724879000).

Almost surely, 2^661005099981 is an apocalyptic number.

It is an amenable number.

661005099981 is a deficient number, since it is larger than the sum of its proper divisors (295693448019).

661005099981 is a wasteful number, since it uses less digits than its factorization.

661005099981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147184896 (or 147184893 counting only the distinct ones).

The product of its (nonzero) digits is 1049760, while the sum is 54.

The spelling of 661005099981 in words is "six hundred sixty-one billion, five million, ninety-nine thousand, nine hundred eighty-one".