1215681 has 4 divisors (see below), whose sum is σ = 1620912. Its totient is φ = 810452.

The previous prime is 1215679. The next prime is 1215703. The reversal of 1215681 is 1865121.

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 1215681 - 2¹ = 1215679 is a prime.

It is a super-2 number, since 2×1215681² = 2955760587522, which contains 22 as substring.

It is a D-number.

1215681 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1215631) 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, 202611 + ... + 202616.

It is an arithmetic number, because the mean of its divisors is an integer number (405228).

2^1215681 is an apocalyptic number.

It is an amenable number.

1215681 is a deficient number, since it is larger than the sum of its proper divisors (405231).

1215681 is an equidigital number, since it uses as much as digits as its factorization.

1215681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 405230.

The product of its digits is 480, while the sum is 24.

The square root of 1215681 is about 1102.5792488524. The cubic root of 1215681 is about 106.7267315786.

The spelling of 1215681 in words is "one million, two hundred fifteen thousand, six hundred eighty-one".