721661501 has 16 divisors (see below), whose sum is σ = 822607488. Its totient is φ = 626683200.

The previous prime is 721661483. The next prime is 721661503. The reversal of 721661501 is 105166127.

It is not a de Polignac number, because 721661501 - 2¹⁰ = 721660477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721661503) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 250811 + ... + 253671.

It is an arithmetic number, because the mean of its divisors is an integer number (51412968).

Almost surely, 2^721661501 is an apocalyptic number.

It is an amenable number.

721661501 is a deficient number, since it is larger than the sum of its proper divisors (100945987).

721661501 is a wasteful number, since it uses less digits than its factorization.

721661501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3892.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 721661501 is about 26863.7581324728. The cubic root of 721661501 is about 896.9698510100.

The spelling of 721661501 in words is "seven hundred twenty-one million, six hundred sixty-one thousand, five hundred one".