28021421 has 2 divisors, whose sum is σ = 28021422. Its totient is φ = 28021420.

The previous prime is 28021403. The next prime is 28021501. The reversal of 28021421 is 12412082.

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., 20376196 + 7645225 = 4514^2 + 2765^2 .

It is a cyclic number.

It is not a de Polignac number, because 28021421 - 2¹⁰ = 28020397 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 28021393 and 28021402.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28021121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14010710 + 14010711.

It is an arithmetic number, because the mean of its divisors is an integer number (14010711).

Almost surely, 2^28021421 is an apocalyptic number.

It is an amenable number.

28021421 is a deficient number, since it is larger than the sum of its proper divisors (1).

28021421 is an equidigital number, since it uses as much as digits as its factorization.

28021421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 28021421 is about 5293.5263293952. The cubic root of 28021421 is about 303.7363140825.

The spelling of 28021421 in words is "twenty-eight million, twenty-one thousand, four hundred twenty-one".