1561401643 has 4 divisors (see below), whose sum is σ = 1561892328. Its totient is φ = 1560910960.

The previous prime is 1561401619. The next prime is 1561401649. The reversal of 1561401643 is 3461041651.

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

It is a cyclic number.

It is not a de Polignac number, because 1561401643 - 2⁹ = 1561401131 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561401649) 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, 240538 + ... + 246943.

It is an arithmetic number, because the mean of its divisors is an integer number (390473082).

Almost surely, 2^1561401643 is an apocalyptic number.

1561401643 is a deficient number, since it is larger than the sum of its proper divisors (490685).

1561401643 is an equidigital number, since it uses as much as digits as its factorization.

1561401643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 490684.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 1561401643 is about 39514.5750704724. The cubic root of 1561401643 is about 1160.1252448498.

The spelling of 1561401643 in words is "one billion, five hundred sixty-one million, four hundred one thousand, six hundred forty-three".