1661120215 has 16 divisors (see below), whose sum is σ = 2020138560. Its totient is φ = 1311137280.

The previous prime is 1661120177. The next prime is 1661120221. The reversal of 1661120215 is 5120211661.

It is a happy number.

It is not a de Polignac number, because 1661120215 - 2¹⁵ = 1661087447 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1661120215.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 125022 + ... + 137668.

It is an arithmetic number, because the mean of its divisors is an integer number (126258660).

Almost surely, 2^1661120215 is an apocalyptic number.

1661120215 is a deficient number, since it is larger than the sum of its proper divisors (359018345).

1661120215 is a wasteful number, since it uses less digits than its factorization.

1661120215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13002.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 1661120215 is about 40756.8425543491. The cubic root of 1661120215 is about 1184.3144307248.

Adding to 1661120215 its reverse (5120211661), we get a palindrome (6781331876).

The spelling of 1661120215 in words is "one billion, six hundred sixty-one million, one hundred twenty thousand, two hundred fifteen".