21121011987 has 16 divisors (see below), whose sum is σ = 29617152000. Its totient is φ = 13362414912.

The previous prime is 21121011959. The next prime is 21121012021. The reversal of 21121011987 is 78911012112.

It is not a de Polignac number, because 21121011987 - 2¹⁸ = 21120749843 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21121011907) 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, 1196362 + ... + 1213887.

It is an arithmetic number, because the mean of its divisors is an integer number (1851072000).

Almost surely, 2^21121011987 is an apocalyptic number.

21121011987 is a deficient number, since it is larger than the sum of its proper divisors (8496140013).

21121011987 is a wasteful number, since it uses less digits than its factorization.

21121011987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2410402.

The product of its (nonzero) digits is 2016, while the sum is 33.

The spelling of 21121011987 in words is "twenty-one billion, one hundred twenty-one million, eleven thousand, nine hundred eighty-seven".