1646618381 has 2 divisors, whose sum is σ = 1646618382. Its totient is φ = 1646618380.

The previous prime is 1646618371. The next prime is 1646618387. The reversal of 1646618381 is 1838166461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1615638025 + 30980356 = 40195^2 + 5566^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1646618381 is a prime.

It is a super-2 number, since 2×1646618381² = 5422704185294122322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1646618387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 823309190 + 823309191.

It is an arithmetic number, because the mean of its divisors is an integer number (823309191).

Almost surely, 2^1646618381 is an apocalyptic number.

It is an amenable number.

1646618381 is a deficient number, since it is larger than the sum of its proper divisors (1).

1646618381 is an equidigital number, since it uses as much as digits as its factorization.

1646618381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165888, while the sum is 44.

The square root of 1646618381 is about 40578.5458216531. The cubic root of 1646618381 is about 1180.8579370703.

The spelling of 1646618381 in words is "one billion, six hundred forty-six million, six hundred eighteen thousand, three hundred eighty-one".