1664961587 has 4 divisors (see below), whose sum is σ = 1667252496. Its totient is φ = 1662670680.

The previous prime is 1664961581. The next prime is 1664961629. The reversal of 1664961587 is 7851694661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7851694661 = 56711 ⋅138451.

It is a cyclic number.

It is not a de Polignac number, because 1664961587 - 2¹² = 1664957491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1664961581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1144364 + ... + 1145817.

It is an arithmetic number, because the mean of its divisors is an integer number (416813124).

Almost surely, 2^1664961587 is an apocalyptic number.

1664961587 is a deficient number, since it is larger than the sum of its proper divisors (2290909).

1664961587 is an equidigital number, since it uses as much as digits as its factorization.

1664961587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2290908.

The product of its digits is 2177280, while the sum is 53.

The square root of 1664961587 is about 40803.9408268368. The cubic root of 1664961587 is about 1185.2266444423.

The spelling of 1664961587 in words is "one billion, six hundred sixty-four million, nine hundred sixty-one thousand, five hundred eighty-seven".