1551278421 has 48 divisors (see below), whose sum is σ = 2802129408. Its totient is φ = 803412000.

The previous prime is 1551278329. The next prime is 1551278423. The reversal of 1551278421 is 1248721551.

It is a happy number.

1551278421 is a `hidden beast` number, since 1 + 551 + 2 + 7 + 84 + 21 = 666.

It is not a de Polignac number, because 1551278421 - 2⁹ = 1551277909 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1551278423) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 237246 + ... + 243696.

It is an arithmetic number, because the mean of its divisors is an integer number (58377696).

Almost surely, 2^1551278421 is an apocalyptic number.

1551278421 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1551278421 is a deficient number, since it is larger than the sum of its proper divisors (1250850987).

1551278421 is a wasteful number, since it uses less digits than its factorization.

1551278421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6822 (or 6819 counting only the distinct ones).

The product of its digits is 22400, while the sum is 36.

The square root of 1551278421 is about 39386.2719865691. The cubic root of 1551278421 is about 1157.6126139409.

Adding to 1551278421 its reverse (1248721551), we get a palindrome (2799999972).

It can be divided in two parts, 1551 and 278421, that added together give a palindrome (279972).

The spelling of 1551278421 in words is "one billion, five hundred fifty-one million, two hundred seventy-eight thousand, four hundred twenty-one".