721620457 has 4 divisors (see below), whose sum is σ = 728765316. Its totient is φ = 714475600.

The previous prime is 721620433. The next prime is 721620461. The reversal of 721620457 is 754026127.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 349091856 + 372528601 = 18684^2 + 19301^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721620457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721626457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3572278 + ... + 3572479.

It is an arithmetic number, because the mean of its divisors is an integer number (182191329).

Almost surely, 2^721620457 is an apocalyptic number.

It is an amenable number.

721620457 is a deficient number, since it is larger than the sum of its proper divisors (7144859).

721620457 is a wasteful number, since it uses less digits than its factorization.

721620457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7144858.

The product of its (nonzero) digits is 23520, while the sum is 34.

The square root of 721620457 is about 26862.9941927552. The cubic root of 721620457 is about 896.9528458405.

It can be divided in two parts, 72 and 1620457, that added together give a square (1620529 = 1273²).

The spelling of 721620457 in words is "seven hundred twenty-one million, six hundred twenty thousand, four hundred fifty-seven".