81544121637 has 8 divisors (see below), whose sum is σ = 118609631520. Its totient is φ = 49420679760.

The previous prime is 81544121621. The next prime is 81544121669. The reversal of 81544121637 is 73612144518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81544121637 - 2⁴ = 81544121621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81544121137) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1235516962 + ... + 1235517027.

It is an arithmetic number, because the mean of its divisors is an integer number (14826203940).

Almost surely, 2^81544121637 is an apocalyptic number.

It is an amenable number.

81544121637 is a deficient number, since it is larger than the sum of its proper divisors (37065509883).

81544121637 is a wasteful number, since it uses less digits than its factorization.

81544121637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2471034003.

The product of its digits is 161280, while the sum is 42.

The spelling of 81544121637 in words is "eighty-one billion, five hundred forty-four million, one hundred twenty-one thousand, six hundred thirty-seven".