216981261 has 36 divisors (see below), whose sum is σ = 378111552. Its totient is φ = 123982488.

The previous prime is 216981253. The next prime is 216981301. The reversal of 216981261 is 162189612.

It is not a de Polignac number, because 216981261 - 2³ = 216981253 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216981211) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 2796 + ... + 21018.

Almost surely, 2^216981261 is an apocalyptic number.

216981261 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

216981261 is a deficient number, since it is larger than the sum of its proper divisors (161130291).

216981261 is an equidigital number, since it uses as much as digits as its factorization.

216981261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18252 (or 18233 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The square root of 216981261 is about 14730.2838058199. The cubic root of 216981261 is about 600.9072026144.

The spelling of 216981261 in words is "two hundred sixteen million, nine hundred eighty-one thousand, two hundred sixty-one".