211215681 has 10 divisors (see below), whose sum is σ = 315519842. Its totient is φ = 140810400.

The previous prime is 211215677. The next prime is 211215689. The reversal of 211215681 is 186512112.

It can be written as a sum of positive squares in only one way, i.e., 176464656 + 34751025 = 13284^2 + 5895^2 .

It is not a de Polignac number, because 211215681 - 2² = 211215677 is a prime.

It is a super-2 number, since 2×211215681² = 89224127800587522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (211215689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1303720 + ... + 1303881.

Almost surely, 2^211215681 is an apocalyptic number.

It is an amenable number.

211215681 is a deficient number, since it is larger than the sum of its proper divisors (104304161).

211215681 is an equidigital number, since it uses as much as digits as its factorization.

211215681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2607613 (or 2607604 counting only the distinct ones).

The product of its digits is 960, while the sum is 27.

The square root of 211215681 is about 14533.2611963042. The cubic root of 211215681 is about 595.5369594278.

Adding to 211215681 its reverse (186512112), we get a palindrome (397727793).

The spelling of 211215681 in words is "two hundred eleven million, two hundred fifteen thousand, six hundred eighty-one".