216721506 has 32 divisors (see below), whose sum is σ = 446460480. Its totient is φ = 70082496.

The previous prime is 216721499. The next prime is 216721517. The reversal of 216721506 is 605127612.

216721506 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×216721506² = 93936422325816072, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 86905 + ... + 89363.

It is an arithmetic number, because the mean of its divisors is an integer number (13951890).

Almost surely, 2^216721506 is an apocalyptic number.

216721506 is an abundant number, since it is smaller than the sum of its proper divisors (229738974).

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

216721506 is a wasteful number, since it uses less digits than its factorization.

216721506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2898.

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 216721506 is about 14721.4641255549. The cubic root of 216721506 is about 600.6673186457.

The spelling of 216721506 in words is "two hundred sixteen million, seven hundred twenty-one thousand, five hundred six".