216405756 has 180 divisors, whose sum is σ = 675519768. Its totient is φ = 60201792.

The previous prime is 216405751. The next prime is 216405769. The reversal of 216405756 is 657504612.

It is a happy number.

216405756 is a `hidden beast` number, since 2 + 1 + 640 + 5 + 7 + 5 + 6 = 666.

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

It is a self number, because there is not a number n which added to its sum of digits gives 216405756.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216405751) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 682510 + ... + 682826.

Almost surely, 2^216405756 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 216405756, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (337759884).

216405756 is an abundant number, since it is smaller than the sum of its proper divisors (459114012).

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

216405756 is a wasteful number, since it uses less digits than its factorization.

216405756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 390 (or 372 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 36.

The square root of 216405756 is about 14710.7360794761. The cubic root of 216405756 is about 600.3754649944.

The spelling of 216405756 in words is "two hundred sixteen million, four hundred five thousand, seven hundred fifty-six".