21216405665426 has 16 divisors (see below), whose sum is σ = 32478401960640. Its totient is φ = 10392175007760.

The previous prime is 21216405665423. The next prime is 21216405665443. The reversal of 21216405665426 is 62456650461212.

It is a super-2 number, since 2×21216405665426² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21216405665423) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 475809896 + ... + 475854483.

It is an arithmetic number, because the mean of its divisors is an integer number (2029900122540).

Almost surely, 2^{21216405665426} is an apocalyptic number.

21216405665426 is a deficient number, since it is larger than the sum of its proper divisors (11261996295214).

21216405665426 is a wasteful number, since it uses less digits than its factorization.

21216405665426 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 951664609.

The product of its (nonzero) digits is 4147200, while the sum is 50.

The spelling of 21216405665426 in words is "twenty-one trillion, two hundred sixteen billion, four hundred five million, six hundred sixty-five thousand, four hundred twenty-six".