6421512665 has 4 divisors (see below), whose sum is σ = 7705815204. Its totient is φ = 5137210128.

The previous prime is 6421512637. The next prime is 6421512673. The reversal of 6421512665 is 5662151246.

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 1025728729 + 5395783936 = 32027^2 + 73456^2 .

It is a cyclic number.

It is not a de Polignac number, because 6421512665 - 2¹⁶ = 6421447129 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 642151262 + ... + 642151271.

It is an arithmetic number, because the mean of its divisors is an integer number (1926453801).

Almost surely, 2^6421512665 is an apocalyptic number.

It is an amenable number.

6421512665 is a deficient number, since it is larger than the sum of its proper divisors (1284302539).

6421512665 is a wasteful number, since it uses less digits than its factorization.

6421512665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1284302538.

The product of its digits is 86400, while the sum is 38.

The square root of 6421512665 is about 80134.3413587458. The cubic root of 6421512665 is about 1858.7134766481.

The spelling of 6421512665 in words is "six billion, four hundred twenty-one million, five hundred twelve thousand, six hundred sixty-five".