97721209 has 2 divisors, whose sum is σ = 97721210. Its totient is φ = 97721208.

The previous prime is 97721201. The next prime is 97721233. The reversal of 97721209 is 90212779.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 57335184 + 40386025 = 7572^2 + 6355^2 .

It is a cyclic number.

It is not a de Polignac number, because 97721209 - 2³ = 97721201 is a prime.

It is not a weakly prime, because it can be changed into another prime (97721201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 48860604 + 48860605.

It is an arithmetic number, because the mean of its divisors is an integer number (48860605).

Almost surely, 2^97721209 is an apocalyptic number.

It is an amenable number.

97721209 is a deficient number, since it is larger than the sum of its proper divisors (1).

97721209 is an equidigital number, since it uses as much as digits as its factorization.

97721209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15876, while the sum is 37.

The square root of 97721209 is about 9885.4038359594. The cubic root of 97721209 is about 460.6060207263.

The spelling of 97721209 in words is "ninety-seven million, seven hundred twenty-one thousand, two hundred nine".