21231011956 has 48 divisors (see below), whose sum is σ = 46397699712. Its totient is φ = 8258342400.

The previous prime is 21231011947. The next prime is 21231011957. The reversal of 21231011956 is 65911013212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231011957) 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, 134176 + ... + 245896.

It is an arithmetic number, because the mean of its divisors is an integer number (966618744).

Almost surely, 2^21231011956 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 21231011956, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23198849856).

21231011956 is an abundant number, since it is smaller than the sum of its proper divisors (25166687756).

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

21231011956 is a wasteful number, since it uses less digits than its factorization.

21231011956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112360 (or 112358 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 31.

The spelling of 21231011956 in words is "twenty-one billion, two hundred thirty-one million, eleven thousand, nine hundred fifty-six".