21001002101001 has 24 divisors (see below), whose sum is σ = 32693807732040. Its totient is φ = 12913573153536.

The previous prime is 21001002100973. The next prime is 21001002101021. The reversal of 21001002101001 is 10010120010012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1465273935225 + 19535728165776 = 1210485^2 + 4419924^2 .

It is not a de Polignac number, because 21001002101001 - 2¹⁸ = 21001001838857 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 (21001002101021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 70130836 + ... + 70429653.

It is an arithmetic number, because the mean of its divisors is an integer number (1362241988835).

Almost surely, 2^{21001002101001} is an apocalyptic number.

It is an amenable number.

21001002101001 is a deficient number, since it is larger than the sum of its proper divisors (11692805631039).

21001002101001 is a wasteful number, since it uses less digits than its factorization.

21001002101001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140561785 (or 140561782 counting only the distinct ones).

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

Adding to 21001002101001 its reverse (10010120010012), we get a palindrome (31011122111013).

The spelling of 21001002101001 in words is "twenty-one trillion, one billion, two million, one hundred one thousand, one".