21679028644 has 81 divisors (see below), whose sum is σ = 47847382947. Its totient is φ = 8565717888.

The previous prime is 21679028621. The next prime is 21679028647. The reversal of 21679028644 is 44682097612.

The square root of 21679028644 is 147238.

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

It can be written as a sum of positive squares in 4 ways, for example, as 37088100 + 21641940544 = 6090^2 + 147112^2 .

It is a Harshad number since it is a multiple of its sum of digits (49).

It is not an unprimeable number, because it can be changed into a prime (21679028647) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 26796912 + ... + 26797720.

Almost surely, 2^21679028644 is an apocalyptic number.

21679028644 is the 147238-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21679028644

21679028644 is an abundant number, since it is smaller than the sum of its proper divisors (26168354303).

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

21679028644 is an equidigital number, since it uses as much as digits as its factorization.

21679028644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1662 (or 831 counting only the distinct ones).

The product of its (nonzero) digits is 1161216, while the sum is 49.

Multiplying 21679028644 by its sum of digits (49), we get a square (1062272403556 = 1030666²).

21679028644 divided by its sum of digits (49) gives a square (442429156 = 21034²).

The spelling of 21679028644 in words is "twenty-one billion, six hundred seventy-nine million, twenty-eight thousand, six hundred forty-four".