1620931681 has 4 divisors (see below), whose sum is σ = 1632593200. Its totient is φ = 1609270164.

The previous prime is 1620931673. The next prime is 1620931687. The reversal of 1620931681 is 1861390261.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1861390261 = 38851 ⋅47911.

It is a cyclic number.

It is not a de Polignac number, because 1620931681 - 2³ = 1620931673 is a prime.

It is a super-3 number, since 3×1620931681³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1620931681.

It is not an unprimeable number, because it can be changed into a prime (1620931687) 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, 5830551 + ... + 5830828.

It is an arithmetic number, because the mean of its divisors is an integer number (408148300).

Almost surely, 2^1620931681 is an apocalyptic number.

It is an amenable number.

1620931681 is a deficient number, since it is larger than the sum of its proper divisors (11661519).

1620931681 is a wasteful number, since it uses less digits than its factorization.

1620931681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11661518.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 1620931681 is about 40260.7958316772. The cubic root of 1620931681 is about 1174.6853978321.

The spelling of 1620931681 in words is "one billion, six hundred twenty million, nine hundred thirty-one thousand, six hundred eighty-one".