1621785317 has 4 divisors (see below), whose sum is σ = 1645991136. Its totient is φ = 1597579500.

The previous prime is 1621785307. The next prime is 1621785349. The reversal of 1621785317 is 7135871261.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 1621785317 - 2²⁸ = 1353349861 is a prime.

It is a super-2 number, since 2×1621785317² = 5260375228873580978, which 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 (1621785307) 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, 12102809 + ... + 12102942.

It is an arithmetic number, because the mean of its divisors is an integer number (411497784).

Almost surely, 2^1621785317 is an apocalyptic number.

It is an amenable number.

1621785317 is a deficient number, since it is larger than the sum of its proper divisors (24205819).

1621785317 is an equidigital number, since it uses as much as digits as its factorization.

1621785317 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24205818.

The product of its digits is 70560, while the sum is 41.

The square root of 1621785317 is about 40271.3957667226. The cubic root of 1621785317 is about 1174.8915709813.

The spelling of 1621785317 in words is "one billion, six hundred twenty-one million, seven hundred eighty-five thousand, three hundred seventeen".