21156851 has 2 divisors, whose sum is σ = 21156852. Its totient is φ = 21156850.

The previous prime is 21156847. The next prime is 21156871. The reversal of 21156851 is 15865112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21156851 - 2² = 21156847 is a prime.

It is a super-2 number, since 2×21156851² = 895224688472402, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21156841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578425 + 10578426.

It is an arithmetic number, because the mean of its divisors is an integer number (10578426).

Almost surely, 2^21156851 is an apocalyptic number.

21156851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21156851 is an equidigital number, since it uses as much as digits as its factorization.

21156851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2400, while the sum is 29.

The square root of 21156851 is about 4599.6577046559. The cubic root of 21156851 is about 276.5776034672.

The spelling of 21156851 in words is "twenty-one million, one hundred fifty-six thousand, eight hundred fifty-one".