21011201001 has 24 divisors (see below), whose sum is σ = 34742932224. Its totient is φ = 11986401600.

The previous prime is 21011200999. The next prime is 21011201011. The reversal of 21011201001 is 10010211012.

It is a happy number.

It is not a de Polignac number, because 21011201001 - 2¹ = 21011200999 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 (21011201011) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 239601 + ... + 315326.

It is an arithmetic number, because the mean of its divisors is an integer number (1447622176).

Almost surely, 2^21011201001 is an apocalyptic number.

21011201001 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21011201001 is a deficient number, since it is larger than the sum of its proper divisors (13731731223).

21011201001 is a wasteful number, since it uses less digits than its factorization.

21011201001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 555541 (or 555538 counting only the distinct ones).

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

Adding to 21011201001 its reverse (10010211012), we get a palindrome (31021412013).

The spelling of 21011201001 in words is "twenty-one billion, eleven million, two hundred one thousand, one".