1321636440 has 64 divisors (see below), whose sum is σ = 4198145760. Its totient is φ = 331704320.

The previous prime is 1321636429. The next prime is 1321636487. The reversal of 1321636440 is 446361231.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 1321636398 and 1321636407.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 321891 + ... + 325970.

Almost surely, 2^1321636440 is an apocalyptic number.

1321636440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1321636440 is an abundant number, since it is smaller than the sum of its proper divisors (2876509320).

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

1321636440 is a wasteful number, since it uses less digits than its factorization.

1321636440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 647892 (or 647888 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 30.

The square root of 1321636440 is about 36354.3180378893. The cubic root of 1321636440 is about 1097.4144342394.

Adding to 1321636440 its reverse (446361231), we get a palindrome (1767997671).

The spelling of 1321636440 in words is "one billion, three hundred twenty-one million, six hundred thirty-six thousand, four hundred forty".