1621781775385 has 8 divisors (see below), whose sum is σ = 1946213580096. Its totient is φ = 1297375120560.

The previous prime is 1621781775379. The next prime is 1621781775389. The reversal of 1621781775385 is 5835771871261.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1621781775385 - 2³⁹ = 1072025961497 is a prime.

It is a super-2 number, since 2×1621781775385² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621781775389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6145311 + ... + 6403780.

It is an arithmetic number, because the mean of its divisors is an integer number (243276697512).

Almost surely, 2^{1621781775385} is an apocalyptic number.

It is an amenable number.

1621781775385 is a deficient number, since it is larger than the sum of its proper divisors (324431804711).

1621781775385 is a wasteful number, since it uses less digits than its factorization.

1621781775385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12574943.

The product of its digits is 19756800, while the sum is 61.

The spelling of 1621781775385 in words is "one trillion, six hundred twenty-one billion, seven hundred eighty-one million, seven hundred seventy-five thousand, three hundred eighty-five".