216787637721 has 4 divisors (see below), whose sum is σ = 289050183632. Its totient is φ = 144525091812.

The previous prime is 216787637713. The next prime is 216787637743. The reversal of 216787637721 is 127736787612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 216787637721 - 2³ = 216787637713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216787637701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36131272951 + ... + 36131272956.

It is an arithmetic number, because the mean of its divisors is an integer number (72262545908).

Almost surely, 2^216787637721 is an apocalyptic number.

It is an amenable number.

216787637721 is a deficient number, since it is larger than the sum of its proper divisors (72262545911).

216787637721 is an equidigital number, since it uses as much as digits as its factorization.

216787637721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72262545910.

The product of its digits is 8297856, while the sum is 57.

The spelling of 216787637721 in words is "two hundred sixteen billion, seven hundred eighty-seven million, six hundred thirty-seven thousand, seven hundred twenty-one".