1645891889 has 4 divisors (see below), whose sum is σ = 1646606400. Its totient is φ = 1645177380.

The previous prime is 1645891883. The next prime is 1645891901. The reversal of 1645891889 is 9881985461.

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 1645891889 - 2¹⁶ = 1645826353 is a prime.

It is a super-2 number, since 2×1645891889² = 5417920220551976642, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1645891883) 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, 353789 + ... + 358410.

It is an arithmetic number, because the mean of its divisors is an integer number (411651600).

Almost surely, 2^1645891889 is an apocalyptic number.

It is an amenable number.

1645891889 is a deficient number, since it is larger than the sum of its proper divisors (714511).

1645891889 is an equidigital number, since it uses as much as digits as its factorization.

1645891889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 714510.

The product of its digits is 4976640, while the sum is 59.

The square root of 1645891889 is about 40569.5931579305. The cubic root of 1645891889 is about 1180.6842457338.

The spelling of 1645891889 in words is "one billion, six hundred forty-five million, eight hundred ninety-one thousand, eight hundred eighty-nine".