21155371 has 2 divisors, whose sum is σ = 21155372. Its totient is φ = 21155370.

The previous prime is 21155369. The next prime is 21155399. The reversal of 21155371 is 17355112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21155371 - 2¹ = 21155369 is a prime.

Together with 21155369, it forms a pair of twin primes.

It is equal to p_1339162 and since 21155371 and 1339162 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21155171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577685 + 10577686.

It is an arithmetic number, because the mean of its divisors is an integer number (10577686).

Almost surely, 2^21155371 is an apocalyptic number.

21155371 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155371 is an equidigital number, since it uses as much as digits as its factorization.

21155371 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1050, while the sum is 25.

The square root of 21155371 is about 4599.4968203055. The cubic root of 21155371 is about 276.5711541080.

The spelling of 21155371 in words is "twenty-one million, one hundred fifty-five thousand, three hundred seventy-one".