21213554606391 has 16 divisors (see below), whose sum is σ = 33440086080000. Its totient is φ = 11704030127328.

The previous prime is 21213554606357. The next prime is 21213554606393. The reversal of 21213554606391 is 19360645531212.

It is not a de Polignac number, because 21213554606391 - 2⁷ = 21213554606263 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21213554606391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213554606393) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17416710891 + ... + 17416712108.

It is an arithmetic number, because the mean of its divisors is an integer number (2090005380000).

Almost surely, 2^{21213554606391} is an apocalyptic number.

21213554606391 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21213554606391 is a deficient number, since it is larger than the sum of its proper divisors (12226531473609).

21213554606391 is a wasteful number, since it uses less digits than its factorization.

21213554606391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34833423038.

The product of its (nonzero) digits is 1166400, while the sum is 48.

The spelling of 21213554606391 in words is "twenty-one trillion, two hundred thirteen billion, five hundred fifty-four million, six hundred six thousand, three hundred ninety-one".