21028001 has 2 divisors, whose sum is σ = 21028002. Its totient is φ = 21028000.

The previous prime is 21027991. The next prime is 21028009. The reversal of 21028001 is 10082012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 5776 = 4585^2 + 76^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21028001 is a prime.

It is not a weakly prime, because it can be changed into another prime (21028009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10514000 + 10514001.

It is an arithmetic number, because the mean of its divisors is an integer number (10514001).

Almost surely, 2^21028001 is an apocalyptic number.

It is an amenable number.

21028001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21028001 is an equidigital number, since it uses as much as digits as its factorization.

21028001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 21028001 is about 4585.6298367836. The cubic root of 21028001 is about 276.0149864088.

The spelling of 21028001 in words is "twenty-one million, twenty-eight thousand, one".