81900040 has 16 divisors (see below), whose sum is σ = 184275180. Its totient is φ = 32760000.

The previous prime is 81900023. The next prime is 81900059. The reversal of 81900040 is 4000918.

It can be written as a sum of positive squares in 2 ways, for example, as 75377124 + 6522916 = 8682^2 + 2554^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81899984 and 81900020.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1023711 + ... + 1023790.

Almost surely, 2^81900040 is an apocalyptic number.

It is an amenable number.

81900040 is an abundant number, since it is smaller than the sum of its proper divisors (102375140).

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

81900040 is a wasteful number, since it uses less digits than its factorization.

81900040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2047512 (or 2047508 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 81900040 is about 9049.8640873772. The cubic root of 81900040 is about 434.2715424986.

Adding to 81900040 its reverse (4000918), we get a palindrome (85900958).

The spelling of 81900040 in words is "eighty-one million, nine hundred thousand, forty".