21404042121 has 64 divisors (see below), whose sum is σ = 37172514816. Its totient is φ = 10622726400.

The previous prime is 21404042119. The next prime is 21404042123. The reversal of 21404042121 is 12124040412.

It is an interprime number because it is at equal distance from previous prime (21404042119) and next prime (21404042123).

It is not a de Polignac number, because 21404042121 - 2¹ = 21404042119 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21404042123) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5635195 + ... + 5638991.

It is an arithmetic number, because the mean of its divisors is an integer number (580820544).

Almost surely, 2^21404042121 is an apocalyptic number.

21404042121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21404042121 is a deficient number, since it is larger than the sum of its proper divisors (15768472695).

21404042121 is a wasteful number, since it uses less digits than its factorization.

21404042121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4902.

The product of its (nonzero) digits is 512, while the sum is 21.

Adding to 21404042121 its reverse (12124040412), we get a palindrome (33528082533).

The spelling of 21404042121 in words is "twenty-one billion, four hundred four million, forty-two thousand, one hundred twenty-one".