81002123136 has 192 divisors, whose sum is σ = 254589931440. Its totient is φ = 24516403200.

The previous prime is 81002123123. The next prime is 81002123173. The reversal of 81002123136 is 63132120018.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (192).

It is a super-2 number, since 2×81002123136² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11920956 + ... + 11927748.

Almost surely, 2^81002123136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81002123136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (127294965720).

81002123136 is an abundant number, since it is smaller than the sum of its proper divisors (173587808304).

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

81002123136 is a wasteful number, since it uses less digits than its factorization.

81002123136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7765 (or 7750 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The spelling of 81002123136 in words is "eighty-one billion, two million, one hundred twenty-three thousand, one hundred thirty-six".