1221210001 has 16 divisors (see below), whose sum is σ = 1435004928. Its totient is φ = 1027659600.

The previous prime is 1221209999. The next prime is 1221210013. The reversal of 1221210001 is 1000121221.

It is not a de Polignac number, because 1221210001 - 2¹ = 1221209999 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1221210001.

It is not an unprimeable number, because it can be changed into a prime (1221210701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 70011 + ... + 85696.

It is an arithmetic number, because the mean of its divisors is an integer number (89687808).

Almost surely, 2^1221210001 is an apocalyptic number.

1221210001 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221210001 is a deficient number, since it is larger than the sum of its proper divisors (213794927).

1221210001 is a wasteful number, since it uses less digits than its factorization.

1221210001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155772.

The product of its (nonzero) digits is 8, while the sum is 10.

The square root of 1221210001 is about 34945.8152144144. The cubic root of 1221210001 is about 1068.8828708143.

Adding to 1221210001 its reverse (1000121221), we get a palindrome (2221331222).

The spelling of 1221210001 in words is "one billion, two hundred twenty-one million, two hundred ten thousand, one".