20100001221 has 24 divisors (see below), whose sum is σ = 31013250840. Its totient is φ = 12500146176.

The previous prime is 20100001127. The next prime is 20100001303. The reversal of 20100001221 is 12210000102.

It can be written as a sum of positive squares in 4 ways, for example, as 4340964996 + 15759036225 = 65886^2 + 125535^2 .

It is not a de Polignac number, because 20100001221 - 2⁹ = 20100000709 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20100001121) 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, 564006 + ... + 598583.

It is an arithmetic number, because the mean of its divisors is an integer number (1292218785).

Almost surely, 2^20100001221 is an apocalyptic number.

It is an amenable number.

20100001221 is a deficient number, since it is larger than the sum of its proper divisors (10913249619).

20100001221 is a wasteful number, since it uses less digits than its factorization.

20100001221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1162725 (or 1162722 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 20100001221 its reverse (12210000102), we get a palindrome (32310001323).

The spelling of 20100001221 in words is "twenty billion, one hundred million, one thousand, two hundred twenty-one".