1664439971 has 2 divisors, whose sum is σ = 1664439972. Its totient is φ = 1664439970.

The previous prime is 1664439943. The next prime is 1664439983. The reversal of 1664439971 is 1799344661.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1664439971 - 2²² = 1660245667 is a prime.

It is not a weakly prime, because it can be changed into another prime (1664439901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832219985 + 832219986.

It is an arithmetic number, because the mean of its divisors is an integer number (832219986).

Almost surely, 2^1664439971 is an apocalyptic number.

1664439971 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664439971 is an equidigital number, since it uses as much as digits as its factorization.

1664439971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 979776, while the sum is 50.

The square root of 1664439971 is about 40797.5485905710. The cubic root of 1664439971 is about 1185.1028582522.

The spelling of 1664439971 in words is "one billion, six hundred sixty-four million, four hundred thirty-nine thousand, nine hundred seventy-one".