72355721 has 2 divisors, whose sum is σ = 72355722. Its totient is φ = 72355720.

The previous prime is 72355711. The next prime is 72355733. The reversal of 72355721 is 12755327.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64176121 + 8179600 = 8011^2 + 2860^2 .

It is a cyclic number.

It is not a de Polignac number, because 72355721 - 2¹⁰ = 72354697 is a prime.

It is a super-2 number, since 2×72355721² = 10470700722859682, which contains 22 as substring.

It is equal to p_4248473 and since 72355721 and 4248473 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (72355711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36177860 + 36177861.

It is an arithmetic number, because the mean of its divisors is an integer number (36177861).

Almost surely, 2^72355721 is an apocalyptic number.

It is an amenable number.

72355721 is a deficient number, since it is larger than the sum of its proper divisors (1).

72355721 is an equidigital number, since it uses as much as digits as its factorization.

72355721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14700, while the sum is 32.

The square root of 72355721 is about 8506.2166090454. The cubic root of 72355721 is about 416.7007593082.

The spelling of 72355721 in words is "seventy-two million, three hundred fifty-five thousand, seven hundred twenty-one".