616721391 has 72 divisors (see below), whose sum is σ = 1088440080. Its totient is φ = 344710080.

The previous prime is 616721389. The next prime is 616721401. The reversal of 616721391 is 193127616.

616721391 is a `hidden beast` number, since 616 + 7 + 2 + 1 + 39 + 1 = 666.

It is not a de Polignac number, because 616721391 - 2¹ = 616721389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (616721311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 551565 + ... + 552681.

Almost surely, 2^616721391 is an apocalyptic number.

616721391 is a deficient number, since it is larger than the sum of its proper divisors (471718689).

616721391 is a wasteful number, since it uses less digits than its factorization.

616721391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1174 (or 1144 counting only the distinct ones).

The product of its digits is 13608, while the sum is 36.

The square root of 616721391 is about 24833.8758755052. The cubic root of 616721391 is about 851.1961894220.

The spelling of 616721391 in words is "six hundred sixteen million, seven hundred twenty-one thousand, three hundred ninety-one".