216991523 has 16 divisors (see below), whose sum is σ = 251712000. Its totient is φ = 183218112.

The previous prime is 216991517. The next prime is 216991529. The reversal of 216991523 is 325199612.

It is an interprime number because it is at equal distance from previous prime (216991517) and next prime (216991529).

It is a de Polignac number, because none of the positive numbers 2^k-216991523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216991529) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 235658 + ... + 236576.

It is an arithmetic number, because the mean of its divisors is an integer number (15732000).

Almost surely, 2^216991523 is an apocalyptic number.

216991523 is a deficient number, since it is larger than the sum of its proper divisors (34720477).

216991523 is an equidigital number, since it uses as much as digits as its factorization.

216991523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1394.

The product of its digits is 29160, while the sum is 38.

The square root of 216991523 is about 14730.6321317179. The cubic root of 216991523 is about 600.9166756482.

The spelling of 216991523 in words is "two hundred sixteen million, nine hundred ninety-one thousand, five hundred twenty-three".