1664686387 has 64 divisors (see below), whose sum is σ = 2307594240. Its totient is φ = 1163289600.

The previous prime is 1664686369. The next prime is 1664686421. The reversal of 1664686387 is 7836864661.

It is a cyclic number.

It is not a de Polignac number, because 1664686387 - 2¹¹ = 1664684339 is a prime.

It is a super-2 number, since 2×1664686387² = 5542361534126227538, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1664686307) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1629937 + ... + 1630957.

It is an arithmetic number, because the mean of its divisors is an integer number (36056160).

Almost surely, 2^1664686387 is an apocalyptic number.

1664686387 is a deficient number, since it is larger than the sum of its proper divisors (642907853).

1664686387 is a wasteful number, since it uses less digits than its factorization.

1664686387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1124.

The product of its digits is 6967296, while the sum is 55.

The square root of 1664686387 is about 40800.5684641771. The cubic root of 1664686387 is about 1185.1613391629.

The spelling of 1664686387 in words is "one billion, six hundred sixty-four million, six hundred eighty-six thousand, three hundred eighty-seven".