21042120405 has 8 divisors (see below), whose sum is σ = 33667392672. Its totient is φ = 11222464208.

The previous prime is 21042120401. The next prime is 21042120427. The reversal of 21042120405 is 50402124012.

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

It is a cyclic number.

It is not a de Polignac number, because 21042120405 - 2² = 21042120401 is a prime.

It is a super-2 number, since 2×21042120405² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042120401) 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, 701403999 + ... + 701404028.

It is an arithmetic number, because the mean of its divisors is an integer number (4208424084).

Almost surely, 2^21042120405 is an apocalyptic number.

It is an amenable number.

21042120405 is a deficient number, since it is larger than the sum of its proper divisors (12625272267).

21042120405 is a wasteful number, since it uses less digits than its factorization.

21042120405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1402808035.

The product of its (nonzero) digits is 640, while the sum is 21.

Adding to 21042120405 its reverse (50402124012), we get a palindrome (71444244417).

The spelling of 21042120405 in words is "twenty-one billion, forty-two million, one hundred twenty thousand, four hundred five".