721019640 has 384 divisors, whose sum is σ = 2647572480. Its totient is φ = 156119040.

The previous prime is 721019633. The next prime is 721019641. The reversal of 721019640 is 46910127.

It is a happy number.

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 = 721019598 and 721019607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721019641) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 5677257 + ... + 5677383.

It is an arithmetic number, because the mean of its divisors is an integer number (6894720).

Almost surely, 2^721019640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721019640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1323786240).

721019640 is an abundant number, since it is smaller than the sum of its proper divisors (1926552840).

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

721019640 is a wasteful number, since it uses less digits than its factorization.

721019640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203 (or 188 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 721019640 is about 26851.8088776157. The cubic root of 721019640 is about 896.7038441458.

Adding to 721019640 its reverse (46910127), we get a palindrome (767929767).

The spelling of 721019640 in words is "seven hundred twenty-one million, nineteen thousand, six hundred forty".