1561657078 has 4 divisors (see below), whose sum is σ = 2342485620. Its totient is φ = 780828538.

The previous prime is 1561657073. The next prime is 1561657087. The reversal of 1561657078 is 8707561651.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561657073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390414268 + ... + 390414271.

It is an arithmetic number, because the mean of its divisors is an integer number (585621405).

Almost surely, 2^1561657078 is an apocalyptic number.

1561657078 is a deficient number, since it is larger than the sum of its proper divisors (780828542).

1561657078 is an equidigital number, since it uses as much as digits as its factorization.

1561657078 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780828541.

The product of its (nonzero) digits is 352800, while the sum is 46.

The square root of 1561657078 is about 39517.8071000910. The cubic root of 1561657078 is about 1160.1885043439.

The spelling of 1561657078 in words is "one billion, five hundred sixty-one million, six hundred fifty-seven thousand, seventy-eight".