21212993 has 2 divisors, whose sum is σ = 21212994. Its totient is φ = 21212992.

The previous prime is 21212977. The next prime is 21213011. The reversal of 21212993 is 39921212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17783089 + 3429904 = 4217^2 + 1852^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212993 - 2⁴ = 21212977 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21212903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606496 + 10606497.

It is an arithmetic number, because the mean of its divisors is an integer number (10606497).

Almost surely, 2^21212993 is an apocalyptic number.

It is an amenable number.

21212993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212993 is an equidigital number, since it uses as much as digits as its factorization.

21212993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1944, while the sum is 29.

The square root of 21212993 is about 4605.7565068075. The cubic root of 21212993 is about 276.8220302849.

The spelling of 21212993 in words is "twenty-one million, two hundred twelve thousand, nine hundred ninety-three".