21427220646 has 96 divisors (see below), whose sum is σ = 52584360192. Its totient is φ = 6259818240.

The previous prime is 21427220641. The next prime is 21427220657. The reversal of 21427220646 is 64602272412.

21427220646 is a `hidden beast` number, since 2 + 1 + 4 + 2 + 7 + 2 + 2 + 0 + 646 = 666.

It is a super-2 number, since 2×21427220646² (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 21427220646.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21427220641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 356596 + ... + 412328.

It is an arithmetic number, because the mean of its divisors is an integer number (547753752).

Almost surely, 2^21427220646 is an apocalyptic number.

21427220646 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21427220646, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26292180096).

21427220646 is an abundant number, since it is smaller than the sum of its proper divisors (31157139546).

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

21427220646 is a wasteful number, since it uses less digits than its factorization.

21427220646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55838 (or 55835 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 36.

The spelling of 21427220646 in words is "twenty-one billion, four hundred twenty-seven million, two hundred twenty thousand, six hundred forty-six".