721994400 has 216 divisors, whose sum is σ = 2566827900. Its totient is φ = 190955520.

The previous prime is 721994393. The next prime is 721994407. The reversal of 721994400 is 4499127.

It is an interprime number because it is at equal distance from previous prime (721994393) and next prime (721994407).

It can be written as a sum of positive squares in 6 ways, for example, as 79067664 + 642926736 = 8892^2 + 25356^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (721994407) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1072464 + ... + 1073136.

Almost surely, 2^721994400 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 721994400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1283413950).

721994400 is an abundant number, since it is smaller than the sum of its proper divisors (1844833500).

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

721994400 is a wasteful number, since it uses less digits than its factorization.

721994400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 848 (or 832 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 721994400 is about 26869.9534796769. The cubic root of 721994400 is about 897.1077524423.

The spelling of 721994400 in words is "seven hundred twenty-one million, nine hundred ninety-four thousand, four hundred".