216721651 has 8 divisors (see below), whose sum is σ = 223937408. Its totient is φ = 209520000.

The previous prime is 216721649. The next prime is 216721679. The reversal of 216721651 is 156127612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 216721651 - 2¹ = 216721649 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216721601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34321 + ... + 40141.

It is an arithmetic number, because the mean of its divisors is an integer number (27992176).

Almost surely, 2^216721651 is an apocalyptic number.

216721651 is a deficient number, since it is larger than the sum of its proper divisors (7215757).

216721651 is a wasteful number, since it uses less digits than its factorization.

216721651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7053.

The product of its digits is 5040, while the sum is 31.

The square root of 216721651 is about 14721.4690503360. The cubic root of 216721651 is about 600.6674526067.

The spelling of 216721651 in words is "two hundred sixteen million, seven hundred twenty-one thousand, six hundred fifty-one".