1647399921 has 16 divisors (see below), whose sum is σ = 2313326400. Its totient is φ = 1039929408.

The previous prime is 1647399913. The next prime is 1647399973. The reversal of 1647399921 is 1299937461.

It is not a de Polignac number, because 1647399921 - 2³ = 1647399913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1647399421) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 125355 + ... + 137871.

It is an arithmetic number, because the mean of its divisors is an integer number (144582900).

Almost surely, 2^1647399921 is an apocalyptic number.

It is an amenable number.

1647399921 is a deficient number, since it is larger than the sum of its proper divisors (665926479).

1647399921 is a wasteful number, since it uses less digits than its factorization.

1647399921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14848.

The product of its digits is 734832, while the sum is 51.

The square root of 1647399921 is about 40588.1746448396. The cubic root of 1647399921 is about 1181.0447323736.

The spelling of 1647399921 in words is "one billion, six hundred forty-seven million, three hundred ninety-nine thousand, nine hundred twenty-one".