9781661544 has 32 divisors (see below), whose sum is σ = 24486000000. Its totient is φ = 3256307712.

The previous prime is 9781661537. The next prime is 9781661611. The reversal of 9781661544 is 4451661879.

It is a super-2 number, since 2×9781661544² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 246544 + ... + 283455.

It is an arithmetic number, because the mean of its divisors is an integer number (765187500).

Almost surely, 2^9781661544 is an apocalyptic number.

It is an amenable number.

9781661544 is an abundant number, since it is smaller than the sum of its proper divisors (14704338456).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9781661544 is a wasteful number, since it uses less digits than its factorization.

9781661544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 530777 (or 530773 counting only the distinct ones).

The product of its digits is 1451520, while the sum is 51.

The square root of 9781661544 is about 98902.2828047968. The cubic root of 9781661544 is about 2138.6393032811.

The spelling of 9781661544 in words is "nine billion, seven hundred eighty-one million, six hundred sixty-one thousand, five hundred forty-four".