1585781690981 has 4 divisors (see below), whose sum is σ = 1587063649932. Its totient is φ = 1584499732032.

The previous prime is 1585781690971. The next prime is 1585781690993. The reversal of 1585781690981 is 1890961875851.

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

It can be written as a sum of positive squares in 2 ways, for example, as 978979640356 + 606802050625 = 989434^2 + 778975^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1585781690981 is a prime.

It is a super-2 number, since 2×1585781690981² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1585781690971) 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, 640977620 + ... + 640980093.

It is an arithmetic number, because the mean of its divisors is an integer number (396765912483).

Almost surely, 2^{1585781690981} is an apocalyptic number.

It is an amenable number.

1585781690981 is a deficient number, since it is larger than the sum of its proper divisors (1281958951).

1585781690981 is a wasteful number, since it uses less digits than its factorization.

1585781690981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1281958950.

The product of its (nonzero) digits is 43545600, while the sum is 68.

The spelling of 1585781690981 in words is "one trillion, five hundred eighty-five billion, seven hundred eighty-one million, six hundred ninety thousand, nine hundred eighty-one".