21205994371 has 16 divisors (see below), whose sum is σ = 22002020064. Its totient is φ = 20422209024.

The previous prime is 21205994357. The next prime is 21205994387. The reversal of 21205994371 is 17349950212.

It is a cyclic number.

It is not a de Polignac number, because 21205994371 - 2⁵ = 21205994339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21205994351) 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, 3454621 + ... + 3460753.

It is an arithmetic number, because the mean of its divisors is an integer number (1375126254).

Almost surely, 2^21205994371 is an apocalyptic number.

21205994371 is a deficient number, since it is larger than the sum of its proper divisors (796025693).

21205994371 is a wasteful number, since it uses less digits than its factorization.

21205994371 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7110.

The product of its (nonzero) digits is 136080, while the sum is 43.

The spelling of 21205994371 in words is "twenty-one billion, two hundred five million, nine hundred ninety-four thousand, three hundred seventy-one".