21029857 has 2 divisors, whose sum is σ = 21029858. Its totient is φ = 21029856.

The previous prime is 21029839. The next prime is 21029951. The reversal of 21029857 is 75892012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10732176 + 10297681 = 3276^2 + 3209^2 .

It is a cyclic number.

It is not a de Polignac number, because 21029857 - 2²³ = 12641249 is a prime.

It is not a weakly prime, because it can be changed into another prime (21029837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10514928 + 10514929.

It is an arithmetic number, because the mean of its divisors is an integer number (10514929).

Almost surely, 2^21029857 is an apocalyptic number.

It is an amenable number.

21029857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21029857 is an equidigital number, since it uses as much as digits as its factorization.

21029857 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 21029857 is about 4585.8322036464. The cubic root of 21029857 is about 276.0231068311.

The spelling of 21029857 in words is "twenty-one million, twenty-nine thousand, eight hundred fifty-seven".