21158471 has 2 divisors, whose sum is σ = 21158472. Its totient is φ = 21158470.

The previous prime is 21158377. The next prime is 21158519. The reversal of 21158471 is 17485112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21158471 - 2¹⁴ = 21142087 is a prime.

It is a super-3 number, since 3×21158471³ (a number of 23 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is equal to p_1339337 and since 21158471 and 1339337 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21158671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10579235 + 10579236.

It is an arithmetic number, because the mean of its divisors is an integer number (10579236).

Almost surely, 2^21158471 is an apocalyptic number.

21158471 is a deficient number, since it is larger than the sum of its proper divisors (1).

21158471 is an equidigital number, since it uses as much as digits as its factorization.

21158471 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2240, while the sum is 29.

The square root of 21158471 is about 4599.8338013454. The cubic root of 21158471 is about 276.5846625562.

The spelling of 21158471 in words is "twenty-one million, one hundred fifty-eight thousand, four hundred seventy-one".