1561001985 has 12 divisors (see below), whose sum is σ = 2705736852. Its totient is φ = 832534368.

The previous prime is 1561001963. The next prime is 1561001987. The reversal of 1561001985 is 5891001651.

1561001985 is a `hidden beast` number, since 1 + 561 + 0 + 0 + 1 + 98 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 164634561 + 1396367424 = 12831^2 + 37368^2 .

It is not a de Polignac number, because 1561001985 - 2¹³ = 1560993793 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1561001987) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17344422 + ... + 17344511.

It is an arithmetic number, because the mean of its divisors is an integer number (225478071).

It is a Proth number, since it is equal to 23819 ⋅ 2¹⁶ + 1 and 23819 < 2¹⁶.

Almost surely, 2^1561001985 is an apocalyptic number.

1561001985 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1561001985 is a deficient number, since it is larger than the sum of its proper divisors (1144734867).

1561001985 is a wasteful number, since it uses less digits than its factorization.

1561001985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34688944 (or 34688941 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 36.

The square root of 1561001985 is about 39509.5176508142. The cubic root of 1561001985 is about 1160.0262541125.

The spelling of 1561001985 in words is "one billion, five hundred sixty-one million, one thousand, nine hundred eighty-five".