216390381 has 4 divisors (see below), whose sum is σ = 288520512. Its totient is φ = 144260252.

The previous prime is 216390353. The next prime is 216390389. The reversal of 216390381 is 183093612.

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 a cyclic number.

It is not a de Polignac number, because 216390381 - 2⁷ = 216390253 is a prime.

It is a super-2 number, since 2×216390381² = 93649593978650322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216390389) 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, 36065061 + ... + 36065066.

It is an arithmetic number, because the mean of its divisors is an integer number (72130128).

Almost surely, 2^216390381 is an apocalyptic number.

It is an amenable number.

216390381 is a deficient number, since it is larger than the sum of its proper divisors (72130131).

216390381 is an equidigital number, since it uses as much as digits as its factorization.

216390381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72130130.

The product of its (nonzero) digits is 7776, while the sum is 33.

The square root of 216390381 is about 14710.2134926724. The cubic root of 216390381 is about 600.3612463470.

The spelling of 216390381 in words is "two hundred sixteen million, three hundred ninety thousand, three hundred eighty-one".