1901661587 has 4 divisors (see below), whose sum is σ = 2173327536. Its totient is φ = 1629995640.

The previous prime is 1901661581. The next prime is 1901661589. The reversal of 1901661587 is 7851661091.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7851661091 = 8363 ⋅938857.

It is not a de Polignac number, because 1901661587 - 2¹⁴ = 1901645203 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1901661581) 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, 135832964 + ... + 135832977.

It is an arithmetic number, because the mean of its divisors is an integer number (543331884).

Almost surely, 2^1901661587 is an apocalyptic number.

1901661587 is a deficient number, since it is larger than the sum of its proper divisors (271665949).

1901661587 is an equidigital number, since it uses as much as digits as its factorization.

1901661587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271665948.

The product of its (nonzero) digits is 90720, while the sum is 44.

The square root of 1901661587 is about 43608.0449802557. The cubic root of 1901661587 is about 1238.9232733920.

The spelling of 1901661587 in words is "one billion, nine hundred one million, six hundred sixty-one thousand, five hundred eighty-seven".