21297899844 has 81 divisors (see below), whose sum is σ = 58327348989. Its totient is φ = 6549697440.

The previous prime is 21297899813. The next prime is 21297899867. The reversal of 21297899844 is 44899879212.

The square root of 21297899844 is 145938.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 3150576900 + 18147322944 = 56130^2 + 134712^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 11382229 + ... + 11384099.

Almost surely, 2^21297899844 is an apocalyptic number.

21297899844 is the 145938-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21297899844

21297899844 is an abundant number, since it is smaller than the sum of its proper divisors (37029449145).

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

21297899844 is a wasteful number, since it uses less digits than its factorization.

21297899844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3778 (or 1889 counting only the distinct ones).

The product of its digits is 20901888, while the sum is 63.

The spelling of 21297899844 in words is "twenty-one billion, two hundred ninety-seven million, eight hundred ninety-nine thousand, eight hundred forty-four".