21205473672 has 64 divisors (see below), whose sum is σ = 54008697600. Its totient is φ = 6936252480.

The previous prime is 21205473671. The next prime is 21205473673. The reversal of 21205473672 is 27637450212.

It is an interprime number because it is at equal distance from previous prime (21205473671) and next prime (21205473673).

It is a super-2 number, since 2×21205473672² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21205473672.

It is not an unprimeable number, because it can be changed into a prime (21205473671) 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, 795423 + ... + 821649.

It is an arithmetic number, because the mean of its divisors is an integer number (843885900).

Almost surely, 2^21205473672 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21205473672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27004348800).

21205473672 is an abundant number, since it is smaller than the sum of its proper divisors (32803223928).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21205473672 is a wasteful number, since it uses less digits than its factorization.

21205473672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26866 (or 26862 counting only the distinct ones).

The product of its (nonzero) digits is 141120, while the sum is 39.

The spelling of 21205473672 in words is "twenty-one billion, two hundred five million, four hundred seventy-three thousand, six hundred seventy-two".