21012012021 has 64 divisors (see below), whose sum is σ = 38325934080. Its totient is φ = 9885507840.

The previous prime is 21012011989. The next prime is 21012012067. The reversal of 21012012021 is 12021021012.

It is not a de Polignac number, because 21012012021 - 2⁵ = 21012011989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21012011988 and 21012012006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012012521) 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, 93150 + ... + 225168.

It is an arithmetic number, because the mean of its divisors is an integer number (598842720).

Almost surely, 2^21012012021 is an apocalyptic number.

21012012021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21012012021 is a deficient number, since it is larger than the sum of its proper divisors (17313922059).

21012012021 is a wasteful number, since it uses less digits than its factorization.

21012012021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132106.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21012012021 its reverse (12021021012), we get a palindrome (33033033033).

The spelling of 21012012021 in words is "twenty-one billion, twelve million, twelve thousand, twenty-one".