4005540 has 216 divisors, whose sum is σ = 16091712. Its totient is φ = 783360.

The previous prime is 4005539. The next prime is 4005553. The reversal of 4005540 is 455004.

Added to its reverse (455004) it gives a square (4460544 = 2112²).

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an Ulam number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 235612 + ... + 235628.

Almost surely, 2^4005540 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 4005540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (8045856).

4005540 is an abundant number, since it is smaller than the sum of its proper divisors (12086172).

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

4005540 is a wasteful number, since it uses less digits than its factorization.

4005540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67 (or 45 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 18.

The square root of 4005540 is about 2001.3845207756. The cubic root of 4005540 is about 158.8133564048.

Adding to 4005540 its reverse (455004), we get a square (4460544 = 2112²).

The spelling of 4005540 in words is "four million, five thousand, five hundred forty".