721781956 has 81 divisors (see below), whose sum is σ = 1566251757. Its totient is φ = 290152800.

The previous prime is 721781941. The next prime is 721781993. The reversal of 721781956 is 659187127.

It is a happy number.

The square root of 721781956 is 26866.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 693479556 + 28302400 = 26334^2 + 5320^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 7146306 + ... + 7146406.

Almost surely, 2^721781956 is an apocalyptic number.

721781956 is a gapful number since it is divisible by the number (76) formed by its first and last digit.

721781956 is the 26866-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721781956

721781956 is an abundant number, since it is smaller than the sum of its proper divisors (844469801).

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

721781956 is a wasteful number, since it uses less digits than its factorization.

721781956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 258 (or 129 counting only the distinct ones).

The product of its digits is 211680, while the sum is 46.

The cubic root of 721781956 is about 897.0197536733.

The spelling of 721781956 in words is "seven hundred twenty-one million, seven hundred eighty-one thousand, nine hundred fifty-six".