21510509987 has 8 divisors (see below), whose sum is σ = 21918577536. Its totient is φ = 21102524352.

The previous prime is 21510509963. The next prime is 21510510029. The reversal of 21510509987 is 78990501512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21510509987 - 2¹⁰ = 21510508963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21510509287) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 885143 + ... + 909119.

It is an arithmetic number, because the mean of its divisors is an integer number (2739822192).

Almost surely, 2^21510509987 is an apocalyptic number.

21510509987 is a deficient number, since it is larger than the sum of its proper divisors (408067549).

21510509987 is a wasteful number, since it uses less digits than its factorization.

21510509987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40957.

The product of its (nonzero) digits is 226800, while the sum is 47.

The spelling of 21510509987 in words is "twenty-one billion, five hundred ten million, five hundred nine thousand, nine hundred eighty-seven".