21205472991 has 8 divisors (see below), whose sum is σ = 28274734464. Its totient is φ = 14136596760.

The previous prime is 21205472987. The next prime is 21205472993. The reversal of 21205472991 is 19927450212.

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

It is not a de Polignac number, because 21205472991 - 2² = 21205472987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205472993) 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, 76350 + ... + 219636.

It is an arithmetic number, because the mean of its divisors is an integer number (3534341808).

Almost surely, 2^21205472991 is an apocalyptic number.

21205472991 is a deficient number, since it is larger than the sum of its proper divisors (7069261473).

21205472991 is a wasteful number, since it uses less digits than its factorization.

21205472991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 192621.

The product of its (nonzero) digits is 90720, while the sum is 42.

The spelling of 21205472991 in words is "twenty-one billion, two hundred five million, four hundred seventy-two thousand, nine hundred ninety-one".