21121001001 has 12 divisors (see below), whose sum is σ = 30678551280. Its totient is φ = 14002003320.

The previous prime is 21121000961. The next prime is 21121001081. The reversal of 21121001001 is 10010012112.

It is a happy number.

It is not a de Polignac number, because 21121001001 - 2⁹ = 21121000489 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is not an unprimeable number, because it can be changed into a prime (21121001081) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6553635 + ... + 6556856.

It is an arithmetic number, because the mean of its divisors is an integer number (2556545940).

Almost surely, 2^21121001001 is an apocalyptic number.

It is an amenable number.

21121001001 is a deficient number, since it is larger than the sum of its proper divisors (9557550279).

21121001001 is a wasteful number, since it uses less digits than its factorization.

21121001001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13110676 (or 13110673 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21121001001 its reverse (10010012112), we get a palindrome (31131013113).

It can be divided in two parts, 2112 and 1001001, that multiplied together give a palindrome (2114114112).

The spelling of 21121001001 in words is "twenty-one billion, one hundred twenty-one million, one thousand, one".