21405354646 has 8 divisors (see below), whose sum is σ = 34577880624. Its totient is φ = 9879394440.

The previous prime is 21405354643. The next prime is 21405354679. The reversal of 21405354646 is 64645350412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21405354599 and 21405354608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405354643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 411641410 + ... + 411641461.

It is an arithmetic number, because the mean of its divisors is an integer number (4322235078).

Almost surely, 2^21405354646 is an apocalyptic number.

21405354646 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21405354646 is a deficient number, since it is larger than the sum of its proper divisors (13172525978).

21405354646 is a wasteful number, since it uses less digits than its factorization.

21405354646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 823282886.

The product of its (nonzero) digits is 345600, while the sum is 40.

The spelling of 21405354646 in words is "twenty-one billion, four hundred five million, three hundred fifty-four thousand, six hundred forty-six".