1251221521 has 4 divisors (see below), whose sum is σ = 1364968944. Its totient is φ = 1137474100.

The previous prime is 1251221483. The next prime is 1251221537.

It is a happy number.

1251221521 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1251221521 - 2⁷ = 1251221393 is a prime.

It is a super-2 number, since 2×1251221521² = 3131110589227106882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1251221492 and 1251221501.

It is not an unprimeable number, because it can be changed into a prime (1251221581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 56873695 + ... + 56873716.

It is an arithmetic number, because the mean of its divisors is an integer number (341242236).

Almost surely, 2^1251221521 is an apocalyptic number.

1251221521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1251221521 is a deficient number, since it is larger than the sum of its proper divisors (113747423).

1251221521 is a wasteful number, since it uses less digits than its factorization.

1251221521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113747422.

The product of its digits is 400, while the sum is 22.

The square root of 1251221521 is about 35372.6097567030. The cubic root of 1251221521 is about 1077.5681224078.

The spelling of 1251221521 in words is "one billion, two hundred fifty-one million, two hundred twenty-one thousand, five hundred twenty-one".