81637140 has 144 divisors (see below), whose sum is σ = 253084608. Its totient is φ = 19648512.

The previous prime is 81637139. The next prime is 81637147. The reversal of 81637140 is 4173618.

81637140 = T₃₄₁ + T₃₄₂ + ... + T₈₀₈.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81637098 and 81637107.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81637147) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 841572 + ... + 841668.

It is an arithmetic number, because the mean of its divisors is an integer number (1757532).

Almost surely, 2^81637140 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 81637140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126542304).

81637140 is an abundant number, since it is smaller than the sum of its proper divisors (171447468).

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

81637140 is a wasteful number, since it uses less digits than its factorization.

81637140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218 (or 203 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 81637140 is about 9035.3273322000. The cubic root of 81637140 is about 433.8063723182.

The spelling of 81637140 in words is "eighty-one million, six hundred thirty-seven thousand, one hundred forty".