21748421 has 2 divisors, whose sum is σ = 21748422. Its totient is φ = 21748420.

The previous prime is 21748399. The next prime is 21748427. The reversal of 21748421 is 12484712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19483396 + 2265025 = 4414^2 + 1505^2 .

It is a cyclic number.

It is not a de Polignac number, because 21748421 - 2¹⁴ = 21732037 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21748427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10874210 + 10874211.

It is an arithmetic number, because the mean of its divisors is an integer number (10874211).

Almost surely, 2^21748421 is an apocalyptic number.

It is an amenable number.

21748421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21748421 is an equidigital number, since it uses as much as digits as its factorization.

21748421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3584, while the sum is 29.

The square root of 21748421 is about 4663.5202369026. The cubic root of 21748421 is about 279.1317534814.

The spelling of 21748421 in words is "twenty-one million, seven hundred forty-eight thousand, four hundred twenty-one".