21042100421 has 8 divisors (see below), whose sum is σ = 22305291480. Its totient is φ = 19781733888.

The previous prime is 21042100399. The next prime is 21042100447. The reversal of 21042100421 is 12400124012.

It can be written as a sum of positive squares in 4 ways, for example, as 17008072225 + 4034028196 = 130415^2 + 63514^2 .

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 21042100421 - 2¹⁸ = 21041838277 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21042100421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042100481) 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, 690776 + ... + 720593.

It is an arithmetic number, because the mean of its divisors is an integer number (2788161435).

Almost surely, 2^21042100421 is an apocalyptic number.

It is an amenable number.

21042100421 is a deficient number, since it is larger than the sum of its proper divisors (1263191059).

21042100421 is a wasteful number, since it uses less digits than its factorization.

21042100421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1412263.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21042100421 its reverse (12400124012), we get a palindrome (33442224433).

The spelling of 21042100421 in words is "twenty-one billion, forty-two million, one hundred thousand, four hundred twenty-one".