21530571987 has 16 divisors (see below), whose sum is σ = 29488170240. Its totient is φ = 13963472352.

The previous prime is 21530571973. The next prime is 21530572013. The reversal of 21530571987 is 78917503512.

It is not a de Polignac number, because 21530571987 - 2¹⁶ = 21530506451 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21530571187) 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, 889714 + ... + 913592.

It is an arithmetic number, because the mean of its divisors is an integer number (1843010640).

Almost surely, 2^21530571987 is an apocalyptic number.

21530571987 is a deficient number, since it is larger than the sum of its proper divisors (7957598253).

21530571987 is a wasteful number, since it uses less digits than its factorization.

21530571987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32042.

The product of its (nonzero) digits is 529200, while the sum is 48.

The spelling of 21530571987 in words is "twenty-one billion, five hundred thirty million, five hundred seventy-one thousand, nine hundred eighty-seven".