21121010001 has 48 divisors (see below), whose sum is σ = 39757221504. Its totient is φ = 10485407232.

The previous prime is 21121009909. The next prime is 21121010017. The reversal of 21121010001 is 10001012112.

It is a happy number.

It is not a de Polignac number, because 21121010001 - 2¹⁵ = 21120977233 is a prime.

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21121010051) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 744571 + ... + 772416.

It is an arithmetic number, because the mean of its divisors is an integer number (828275448).

Almost surely, 2^21121010001 is an apocalyptic number.

21121010001 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21121010001 is a deficient number, since it is larger than the sum of its proper divisors (18636211503).

21121010001 is a wasteful number, since it uses less digits than its factorization.

21121010001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1517030 (or 1517027 counting only the distinct ones).

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

Adding to 21121010001 its reverse (10001012112), we get a palindrome (31122022113).

The spelling of 21121010001 in words is "twenty-one billion, one hundred twenty-one million, ten thousand, one".