1561891604 has 24 divisors (see below), whose sum is σ = 3364075008. Its totient is φ = 617891040.

The previous prime is 1561891589. The next prime is 1561891633. The reversal of 1561891604 is 4061981651.

It is a Smith number, since the sum of its digits (41) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2145092 + ... + 2145819.

It is an arithmetic number, because the mean of its divisors is an integer number (140169792).

Almost surely, 2^1561891604 is an apocalyptic number.

1561891604 is a gapful number since it is divisible by the number (14) formed by its first and last digit.

It is an amenable number.

1561891604 is an abundant number, since it is smaller than the sum of its proper divisors (1802183404).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1561891604 is a wasteful number, since it uses less digits than its factorization.

1561891604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4290935 (or 4290933 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 41.

The square root of 1561891604 is about 39520.7743345193. The cubic root of 1561891604 is about 1160.2465795669.

The spelling of 1561891604 in words is "one billion, five hundred sixty-one million, eight hundred ninety-one thousand, six hundred four".