20101220021 has 4 divisors (see below), whose sum is σ = 20259497472. Its totient is φ = 19942942572.

The previous prime is 20101220011. The next prime is 20101220099. The reversal of 20101220021 is 12002210102.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12002210102 = 2 ⋅6001105051.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20101220021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20101219984 and 20101220011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20101220011) 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, 79138535 + ... + 79138788.

It is an arithmetic number, because the mean of its divisors is an integer number (5064874368).

Almost surely, 2^20101220021 is an apocalyptic number.

It is an amenable number.

20101220021 is a deficient number, since it is larger than the sum of its proper divisors (158277451).

20101220021 is a wasteful number, since it uses less digits than its factorization.

20101220021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158277450.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 20101220021 its reverse (12002210102), we get a palindrome (32103430123).

The spelling of 20101220021 in words is "twenty billion, one hundred one million, two hundred twenty thousand, twenty-one".