21591993213 has 24 divisors (see below), whose sum is σ = 35724431808. Its totient is φ = 12310414272.

The previous prime is 21591993209. The next prime is 21591993287. The reversal of 21591993213 is 31239919512.

21591993213 is a `hidden beast` number, since 21 + 591 + 9 + 9 + 32 + 1 + 3 = 666.

It is not a de Polignac number, because 21591993213 - 2² = 21591993209 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21591994213) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 358920 + ... + 414737.

It is an arithmetic number, because the mean of its divisors is an integer number (1488517992).

Almost surely, 2^21591993213 is an apocalyptic number.

It is an amenable number.

21591993213 is a deficient number, since it is larger than the sum of its proper divisors (14132438595).

21591993213 is a wasteful number, since it uses less digits than its factorization.

21591993213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 774113 (or 774110 counting only the distinct ones).

The product of its digits is 131220, while the sum is 45.

The spelling of 21591993213 in words is "twenty-one billion, five hundred ninety-one million, nine hundred ninety-three thousand, two hundred thirteen".