21155149 has 2 divisors, whose sum is σ = 21155150. Its totient is φ = 21155148.

The previous prime is 21155131. The next prime is 21155159. The reversal of 21155149 is 94155112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19758025 + 1397124 = 4445^2 + 1182^2 .

It is a cyclic number.

It is not a de Polignac number, because 21155149 - 2⁵ = 21155117 is a prime.

It is equal to p_1339147 and since 21155149 and 1339147 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 (21155119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577574 + 10577575.

It is an arithmetic number, because the mean of its divisors is an integer number (10577575).

Almost surely, 2^21155149 is an apocalyptic number.

It is an amenable number.

21155149 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155149 is an equidigital number, since it uses as much as digits as its factorization.

21155149 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1800, while the sum is 28.

The square root of 21155149 is about 4599.4726871675. The cubic root of 21155149 is about 276.5701866782.

It can be divided in two parts, 211551 and 49, that added together give a square (211600 = 460²).

The spelling of 21155149 in words is "twenty-one million, one hundred fifty-five thousand, one hundred forty-nine".