1551221645 has 4 divisors (see below), whose sum is σ = 1861465980. Its totient is φ = 1240977312.

The previous prime is 1551221599. The next prime is 1551221663. The reversal of 1551221645 is 5461221551.

1551221645 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5461221551 = 3727 ⋅1465313.

It can be written as a sum of positive squares in 2 ways, for example, as 238826116 + 1312395529 = 15454^2 + 36227^2 .

It is a cyclic number.

It is not a de Polignac number, because 1551221645 - 2²² = 1547027341 is a prime.

It is a super-3 number, since 3×1551221645³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 155122160 + ... + 155122169.

It is an arithmetic number, because the mean of its divisors is an integer number (465366495).

Almost surely, 2^1551221645 is an apocalyptic number.

It is an amenable number.

1551221645 is a deficient number, since it is larger than the sum of its proper divisors (310244335).

1551221645 is an equidigital number, since it uses as much as digits as its factorization.

1551221645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310244334.

The product of its digits is 12000, while the sum is 32.

The square root of 1551221645 is about 39385.5512212283. The cubic root of 1551221645 is about 1157.5984910913.

The spelling of 1551221645 in words is "one billion, five hundred fifty-one million, two hundred twenty-one thousand, six hundred forty-five".