1491871657 has 2 divisors, whose sum is σ = 1491871658. Its totient is φ = 1491871656.

The previous prime is 1491871651. The next prime is 1491871687. The reversal of 1491871657 is 7561781941.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 908359321 + 583512336 = 30139^2 + 24156^2 .

It is a cyclic number.

It is not a de Polignac number, because 1491871657 - 2³ = 1491871649 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1491871657.

It is not a weakly prime, because it can be changed into another prime (1491871651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 745935828 + 745935829.

It is an arithmetic number, because the mean of its divisors is an integer number (745935829).

Almost surely, 2^1491871657 is an apocalyptic number.

It is an amenable number.

1491871657 is a deficient number, since it is larger than the sum of its proper divisors (1).

1491871657 is an equidigital number, since it uses as much as digits as its factorization.

1491871657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 423360, while the sum is 49.

The square root of 1491871657 is about 38624.7544587665. The cubic root of 1491871657 is about 1142.6428008378.

The spelling of 1491871657 in words is "one billion, four hundred ninety-one million, eight hundred seventy-one thousand, six hundred fifty-seven".