21401993 has 2 divisors, whose sum is σ = 21401994. Its totient is φ = 21401992.

The previous prime is 21401987. The next prime is 21402013. The reversal of 21401993 is 39910412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14500864 + 6901129 = 3808^2 + 2627^2 .

It is a cyclic number.

It is not a de Polignac number, because 21401993 - 2²⁴ = 4624777 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21401903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10700996 + 10700997.

It is an arithmetic number, because the mean of its divisors is an integer number (10700997).

Almost surely, 2^21401993 is an apocalyptic number.

It is an amenable number.

21401993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21401993 is an equidigital number, since it uses as much as digits as its factorization.

21401993 is an evil number, because the sum of its binary digits is even.

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

The square root of 21401993 is about 4626.2288097326. The cubic root of 21401993 is about 277.6417283220.

The spelling of 21401993 in words is "twenty-one million, four hundred one thousand, nine hundred ninety-three".