21421693 has 2 divisors, whose sum is σ = 21421694. Its totient is φ = 21421692.

The previous prime is 21421681. The next prime is 21421703. The reversal of 21421693 is 39612412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12766329 + 8655364 = 3573^2 + 2942^2 .

It is a cyclic number.

It is not a de Polignac number, because 21421693 - 2²¹ = 19324541 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21421793) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710846 + 10710847.

It is an arithmetic number, because the mean of its divisors is an integer number (10710847).

Almost surely, 2^21421693 is an apocalyptic number.

It is an amenable number.

21421693 is a deficient number, since it is larger than the sum of its proper divisors (1).

21421693 is an equidigital number, since it uses as much as digits as its factorization.

21421693 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 28.

The square root of 21421693 is about 4628.3574840325. The cubic root of 21421693 is about 277.7268896232.

The spelling of 21421693 in words is "twenty-one million, four hundred twenty-one thousand, six hundred ninety-three".