1561651321 has 8 divisors (see below), whose sum is σ = 1573983488. Its totient is φ = 1549368000.

The previous prime is 1561651303. The next prime is 1561651349. The reversal of 1561651321 is 1231561651.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1561651321 - 2⁹ = 1561650809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561651361) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53356 + ... + 77266.

It is an arithmetic number, because the mean of its divisors is an integer number (196747936).

Almost surely, 2^1561651321 is an apocalyptic number.

It is an amenable number.

1561651321 is a deficient number, since it is larger than the sum of its proper divisors (12332167).

1561651321 is a wasteful number, since it uses less digits than its factorization.

1561651321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24423.

The product of its digits is 5400, while the sum is 31.

The square root of 1561651321 is about 39517.7342594436. The cubic root of 1561651321 is about 1160.1870786759.

The spelling of 1561651321 in words is "one billion, five hundred sixty-one million, six hundred fifty-one thousand, three hundred twenty-one".