216506401 has 2 divisors, whose sum is σ = 216506402. Its totient is φ = 216506400.

The previous prime is 216506399. The next prime is 216506417. The reversal of 216506401 is 104605612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 142563600 + 73942801 = 11940^2 + 8599^2 .

It is a cyclic number.

It is not a de Polignac number, because 216506401 - 2¹ = 216506399 is a prime.

Together with 216506399, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (216506461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108253200 + 108253201.

It is an arithmetic number, because the mean of its divisors is an integer number (108253201).

Almost surely, 2^216506401 is an apocalyptic number.

It is an amenable number.

216506401 is a deficient number, since it is larger than the sum of its proper divisors (1).

216506401 is an equidigital number, since it uses as much as digits as its factorization.

216506401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 216506401 is about 14714.1564827889. The cubic root of 216506401 is about 600.4685238619.

The spelling of 216506401 in words is "two hundred sixteen million, five hundred six thousand, four hundred one".