1215661 has 4 divisors (see below), whose sum is σ = 1238652. Its totient is φ = 1192672.

The previous prime is 1215649. The next prime is 1215673. The reversal of 1215661 is 1665121.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (1215649) and next prime (1215673).

It can be written as a sum of positive squares in 2 ways, for example, as 585225 + 630436 = 765^2 + 794^2 .

It is a cyclic number.

It is not a de Polignac number, because 1215661 - 2⁵ = 1215629 is a prime.

It is a Duffinian number.

1215661 is a lucky number.

It is a congruent 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, 11416 + ... + 11521.

It is an arithmetic number, because the mean of its divisors is an integer number (309663).

2^1215661 is an apocalyptic number.

It is an amenable number.

1215661 is a deficient number, since it is larger than the sum of its proper divisors (22991).

1215661 is an equidigital number, since it uses as much as digits as its factorization.

1215661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22990.

The product of its digits is 360, while the sum is 22.

The square root of 1215661 is about 1102.5701791723. The cubic root of 1215661 is about 106.7261462972.

The spelling of 1215661 in words is "one million, two hundred fifteen thousand, six hundred sixty-one".