1321521720 has 32 divisors (see below), whose sum is σ = 3964565520. Its totient is φ = 352405760.

The previous prime is 1321521713. The next prime is 1321521727. The reversal of 1321521720 is 271251231.

It is an interprime number because it is at equal distance from previous prime (1321521713) and next prime (1321521727).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1321521727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5506221 + ... + 5506460.

Almost surely, 2^1321521720 is an apocalyptic number.

1321521720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1321521720 is an abundant number, since it is smaller than the sum of its proper divisors (2643043800).

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

1321521720 is a wasteful number, since it uses less digits than its factorization.

1321521720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11012695 (or 11012691 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 1321521720 is about 36352.7401993302. The cubic root of 1321521720 is about 1097.3826809213.

Adding to 1321521720 its reverse (271251231), we get a palindrome (1592772951).

The spelling of 1321521720 in words is "one billion, three hundred twenty-one million, five hundred twenty-one thousand, seven hundred twenty".