216947989 has 2 divisors, whose sum is σ = 216947990. Its totient is φ = 216947988.

The previous prime is 216947977. The next prime is 216947993. The reversal of 216947989 is 989749612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 205779025 + 11168964 = 14345^2 + 3342^2 .

It is a cyclic number.

It is not a de Polignac number, because 216947989 - 2¹¹ = 216945941 is a prime.

It is a super-2 number, since 2×216947989² = 94132859862288242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216947089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108473994 + 108473995.

It is an arithmetic number, because the mean of its divisors is an integer number (108473995).

Almost surely, 2^216947989 is an apocalyptic number.

It is an amenable number.

216947989 is a deficient number, since it is larger than the sum of its proper divisors (1).

216947989 is an equidigital number, since it uses as much as digits as its factorization.

216947989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1959552, while the sum is 55.

The square root of 216947989 is about 14729.1543884909. The cubic root of 216947989 is about 600.8764865879.

The spelling of 216947989 in words is "two hundred sixteen million, nine hundred forty-seven thousand, nine hundred eighty-nine".