1620778205 has 8 divisors (see below), whose sum is σ = 1951071192. Its totient is φ = 1292531008.

The previous prime is 1620778183. The next prime is 1620778207. The reversal of 1620778205 is 5028770261.

It can be written as a sum of positive squares in 4 ways, for example, as 123165604 + 1497612601 = 11098^2 + 38699^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 1620778205 - 2²² = 1616583901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1620778207) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 509702 + ... + 512871.

It is an arithmetic number, because the mean of its divisors is an integer number (243883899).

Almost surely, 2^1620778205 is an apocalyptic number.

It is an amenable number.

1620778205 is a deficient number, since it is larger than the sum of its proper divisors (330292987).

1620778205 is a wasteful number, since it uses less digits than its factorization.

1620778205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1022895.

The product of its (nonzero) digits is 47040, while the sum is 38.

The square root of 1620778205 is about 40258.8897636286. The cubic root of 1620778205 is about 1174.6483220959.

The spelling of 1620778205 in words is "one billion, six hundred twenty million, seven hundred seventy-eight thousand, two hundred five".