987664921 has 4 divisors (see below), whose sum is σ = 994874292. Its totient is φ = 980455552.

The previous prime is 987664913. The next prime is 987664943. The reversal of 987664921 is 129466789.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 273439296 + 714225625 = 16536^2 + 26725^2 .

It is a cyclic number.

It is not a de Polignac number, because 987664921 - 2³ = 987664913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (987664901) 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, 3604480 + ... + 3604753.

It is an arithmetic number, because the mean of its divisors is an integer number (248718573).

Almost surely, 2^987664921 is an apocalyptic number.

It is an amenable number.

987664921 is a deficient number, since it is larger than the sum of its proper divisors (7209371).

987664921 is a wasteful number, since it uses less digits than its factorization.

987664921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7209370.

The product of its digits is 1306368, while the sum is 52.

The square root of 987664921 is about 31427.1366974467. The cubic root of 987664921 is about 995.8712841653.

The spelling of 987664921 in words is "nine hundred eighty-seven million, six hundred sixty-four thousand, nine hundred twenty-one".