1521640 has 32 divisors (see below), whose sum is σ = 3465000. Its totient is φ = 601344.

The previous prime is 1521629. The next prime is 1521643. The reversal of 1521640 is 461251.

1521640 is a nontrivial binomial coefficient, being equal to C(1745, 2).

It can be written as a sum of positive squares in 4 ways, for example, as 1435204 + 86436 = 1198^2 + 294^2 .

It is not an unprimeable number, because it can be changed into a prime (1521643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4186 + ... + 4534.

2^1521640 is an apocalyptic number.

1521640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1521640 is the 1744-th triangular number.

1521640 is the 582-nd centered nonagonal number.

It is an amenable number.

1521640 is an abundant number, since it is smaller than the sum of its proper divisors (1943360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1521640 is a wasteful number, since it uses less digits than its factorization.

1521640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469 (or 465 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 1521640 is about 1233.5477291131. The cubic root of 1521640 is about 115.0192784315.

Adding to 1521640 its reverse (461251), we get a palindrome (1982891).

The spelling of 1521640 in words is "one million, five hundred twenty-one thousand, six hundred forty".