21078851 has 2 divisors, whose sum is σ = 21078852. Its totient is φ = 21078850.

The previous prime is 21078829. The next prime is 21078857. The reversal of 21078851 is 15887012.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21078851 - 2²² = 16884547 is a prime.

It is not a weakly prime, because it can be changed into another prime (21078857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10539425 + 10539426.

It is an arithmetic number, because the mean of its divisors is an integer number (10539426).

Almost surely, 2^21078851 is an apocalyptic number.

21078851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21078851 is an equidigital number, since it uses as much as digits as its factorization.

21078851 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21078851 is about 4591.1709835291. The cubic root of 21078851 is about 276.2372941748.

The spelling of 21078851 in words is "twenty-one million, seventy-eight thousand, eight hundred fifty-one".