72215621 has 4 divisors (see below), whose sum is σ = 72247692. Its totient is φ = 72183552.

The previous prime is 72215617. The next prime is 72215659. The reversal of 72215621 is 12651227.

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 70324996 + 1890625 = 8386^2 + 1375^2 .

It is a cyclic number.

It is not a de Polignac number, because 72215621 - 2² = 72215617 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 (72215021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12380 + ... + 17253.

It is an arithmetic number, because the mean of its divisors is an integer number (18061923).

Almost surely, 2^72215621 is an apocalyptic number.

It is an amenable number.

72215621 is a deficient number, since it is larger than the sum of its proper divisors (32071).

72215621 is a wasteful number, since it uses less digits than its factorization.

72215621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32070.

The product of its digits is 1680, while the sum is 26.

The square root of 72215621 is about 8497.9774652561. The cubic root of 72215621 is about 416.4316375499.

Adding to 72215621 its reverse (12651227), we get a palindrome (84866848).

The spelling of 72215621 in words is "seventy-two million, two hundred fifteen thousand, six hundred twenty-one".