1643897026 has 4 divisors (see below), whose sum is σ = 2465845542. Its totient is φ = 821948512.

The previous prime is 1643896997. The next prime is 1643897027. The reversal of 1643897026 is 6207983461.

It is a Cunningham number, because it is equal to 40545²+1.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6207983461 = 31 ⋅200257531.

It can be written as a sum of positive squares in only one way, i.e., 1643897025 + 1 = 40545^2 + 1^2 .

It is not an unprimeable number, because it can be changed into a prime (1643897027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410974255 + ... + 410974258.

Almost surely, 2^1643897026 is an apocalyptic number.

1643897026 is a deficient number, since it is larger than the sum of its proper divisors (821948516).

1643897026 is an equidigital number, since it uses as much as digits as its factorization.

1643897026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 821948515.

The product of its (nonzero) digits is 435456, while the sum is 46.

The square root of 1643897026 is about 40545.0000123320. Note that the first 4 decimals coincide. The cubic root of 1643897026 is about 1180.2070464037.

The spelling of 1643897026 in words is "one billion, six hundred forty-three million, eight hundred ninety-seven thousand, twenty-six".