20387551491 has 24 divisors (see below), whose sum is σ = 29572373376. Its totient is φ = 13534690560.

The previous prime is 20387551487. The next prime is 20387551501. The reversal of 20387551491 is 19415578302.

20387551491 is a `hidden beast` number, since 2 + 0 + 3 + 8 + 7 + 551 + 4 + 91 = 666.

It is not a de Polignac number, because 20387551491 - 2² = 20387551487 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (20387551991) 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 23 ways as a sum of consecutive naturals, for example, 4805131 + ... + 4809371.

It is an arithmetic number, because the mean of its divisors is an integer number (1232182224).

Almost surely, 2^20387551491 is an apocalyptic number.

20387551491 is a deficient number, since it is larger than the sum of its proper divisors (9184821885).

20387551491 is a wasteful number, since it uses less digits than its factorization.

20387551491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6363 (or 6360 counting only the distinct ones).

The product of its (nonzero) digits is 302400, while the sum is 45.

The spelling of 20387551491 in words is "twenty billion, three hundred eighty-seven million, five hundred fifty-one thousand, four hundred ninety-one".