216851405 has 16 divisors (see below), whose sum is σ = 275937840. Its totient is φ = 163034112.

The previous prime is 216851387. The next prime is 216851449. The reversal of 216851405 is 504158612.

It can be written as a sum of positive squares in 8 ways, for example, as 44769481 + 172081924 = 6691^2 + 13118^2 .

It is a cyclic number.

It is not a de Polignac number, because 216851405 - 2¹⁶ = 216785869 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 73091 + ... + 75999.

It is an arithmetic number, because the mean of its divisors is an integer number (17246115).

Almost surely, 2^216851405 is an apocalyptic number.

It is an amenable number.

216851405 is a deficient number, since it is larger than the sum of its proper divisors (59086435).

216851405 is a wasteful number, since it uses less digits than its factorization.

216851405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3808.

The product of its (nonzero) digits is 9600, while the sum is 32.

The square root of 216851405 is about 14725.8753559848. The cubic root of 216851405 is about 600.7873044307.

The spelling of 216851405 in words is "two hundred sixteen million, eight hundred fifty-one thousand, four hundred five".