1906721865 has 24 divisors (see below), whose sum is σ = 3307941000. Its totient is φ = 1016008704.

The previous prime is 1906721863. The next prime is 1906721879. The reversal of 1906721865 is 5681276091.

It can be written as a sum of positive squares in 4 ways, for example, as 124277904 + 1782443961 = 11148^2 + 42219^2 .

It is not a de Polignac number, because 1906721865 - 2¹ = 1906721863 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 1906721865.

It is not an unprimeable number, because it can be changed into a prime (1906721863) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 33511 + ... + 70259.

It is an arithmetic number, because the mean of its divisors is an integer number (137830875).

Almost surely, 2^1906721865 is an apocalyptic number.

1906721865 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1906721865 is a deficient number, since it is larger than the sum of its proper divisors (1401219135).

1906721865 is a wasteful number, since it uses less digits than its factorization.

1906721865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37913 (or 37910 counting only the distinct ones).

The product of its (nonzero) digits is 181440, while the sum is 45.

The square root of 1906721865 is about 43666.0264393269. The cubic root of 1906721865 is about 1240.0212156013.

The spelling of 1906721865 in words is "one billion, nine hundred six million, seven hundred twenty-one thousand, eight hundred sixty-five".