1251021001 has 4 divisors (see below), whose sum is σ = 1271529604. Its totient is φ = 1230512400.

The previous prime is 1251020999. The next prime is 1251021017. The reversal of 1251021001 is 1001201521.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 60840000 + 1190181001 = 7800^2 + 34499^2 .

It is a cyclic number.

It is not a de Polignac number, because 1251021001 - 2¹ = 1251020999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1251021061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10254210 + ... + 10254331.

It is an arithmetic number, because the mean of its divisors is an integer number (317882401).

Almost surely, 2^1251021001 is an apocalyptic number.

It is an amenable number.

1251021001 is a deficient number, since it is larger than the sum of its proper divisors (20508603).

1251021001 is an equidigital number, since it uses as much as digits as its factorization.

1251021001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20508602.

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 1251021001 is about 35369.7752466707. The cubic root of 1251021001 is about 1077.5105558619.

Adding to 1251021001 its reverse (1001201521), we get a palindrome (2252222522).

The spelling of 1251021001 in words is "one billion, two hundred fifty-one million, twenty-one thousand, one".