81980040 has 64 divisors (see below), whose sum is σ = 247248000. Its totient is φ = 21745152.

The previous prime is 81980011. The next prime is 81980047. The reversal of 81980040 is 4008918.

It is a happy number.

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

It is not an unprimeable number, because it can be changed into a prime (81980047) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22164 + ... + 25596.

It is an arithmetic number, because the mean of its divisors is an integer number (3863250).

Almost surely, 2^81980040 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 81980040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (123624000).

81980040 is an abundant number, since it is smaller than the sum of its proper divisors (165267960).

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

81980040 is a wasteful number, since it uses less digits than its factorization.

81980040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3646 (or 3642 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 81980040 is about 9054.2829644318. The cubic root of 81980040 is about 434.4128953706.

Adding to 81980040 its reverse (4008918), we get a palindrome (85988958).

It can be divided in two parts, 819800 and 40, that added together give a triangular number (819840 = T₁₂₈₀).

The spelling of 81980040 in words is "eighty-one million, nine hundred eighty thousand, forty".