21020042121 has 8 divisors (see below), whose sum is σ = 30182624640. Its totient is φ = 12935410512.

The previous prime is 21020042119. The next prime is 21020042149. The reversal of 21020042121 is 12124002012.

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

It is not a de Polignac number, because 21020042121 - 2¹ = 21020042119 is a prime.

It is a super-2 number, since 2×21020042121² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21020042121.

It is not an unprimeable number, because it can be changed into a prime (21020042111) 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, 269487681 + ... + 269487758.

It is an arithmetic number, because the mean of its divisors is an integer number (3772828080).

Almost surely, 2^21020042121 is an apocalyptic number.

It is an amenable number.

21020042121 is a deficient number, since it is larger than the sum of its proper divisors (9162582519).

21020042121 is a wasteful number, since it uses less digits than its factorization.

21020042121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 538975455.

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 21020042121 its reverse (12124002012), we get a palindrome (33144044133).

The spelling of 21020042121 in words is "twenty-one billion, twenty million, forty-two thousand, one hundred twenty-one".