21406213064 has 8 divisors (see below), whose sum is σ = 40136649510. Its totient is φ = 10703106528.

The previous prime is 21406213057. The next prime is 21406213069. The reversal of 21406213064 is 46031260412.

It can be written as a sum of positive squares in only one way, i.e., 20265800164 + 1140412900 = 142358^2 + 33770^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (21406213069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1337888309 + ... + 1337888324.

Almost surely, 2^21406213064 is an apocalyptic number.

It is an amenable number.

21406213064 is a deficient number, since it is larger than the sum of its proper divisors (18730436446).

21406213064 is a wasteful number, since it uses less digits than its factorization.

21406213064 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2675776639 (or 2675776635 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 29.

Adding to 21406213064 its reverse (46031260412), we get a palindrome (67437473476).

The spelling of 21406213064 in words is "twenty-one billion, four hundred six million, two hundred thirteen thousand, sixty-four".