21000158991 has 12 divisors (see below), whose sum is σ = 34666929232. Its totient is φ = 12000090816.

The previous prime is 21000158989. The next prime is 21000159023. The reversal of 21000158991 is 19985100012.

It is not a de Polignac number, because 21000158991 - 2¹ = 21000158989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000158591) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 166667866 + ... + 166667991.

Almost surely, 2^21000158991 is an apocalyptic number.

21000158991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21000158991 is a deficient number, since it is larger than the sum of its proper divisors (13666770241).

21000158991 is a wasteful number, since it uses less digits than its factorization.

21000158991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333335870 (or 333335867 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 36.

The spelling of 21000158991 in words is "twenty-one billion, one hundred fifty-eight thousand, nine hundred ninety-one".