81561047040 has 1248 divisors, whose sum is σ = 338847909120. Its totient is φ = 18555863040.

The previous prime is 81561046997. The next prime is 81561047123. The reversal of 81561047040 is 4074016518.

It is a happy number.

It is a super-2 number, since 2×81561047040² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81561046986 and 81561047004.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1538887654 + ... + 1538887706.

Almost surely, 2^81561047040 is an apocalyptic number.

81561047040 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81561047040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (169423954560).

81561047040 is an abundant number, since it is smaller than the sum of its proper divisors (257286862080).

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

81561047040 is a wasteful number, since it uses less digits than its factorization.

81561047040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136 (or 97 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The spelling of 81561047040 in words is "eighty-one billion, five hundred sixty-one million, forty-seven thousand, forty".