21315109 has 2 divisors, whose sum is σ = 21315110. Its totient is φ = 21315108.

The previous prime is 21315101. The next prime is 21315137. The reversal of 21315109 is 90151312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21068100 + 247009 = 4590^2 + 497^2 .

It is a cyclic number.

It is not a de Polignac number, because 21315109 - 2³ = 21315101 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21315109.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21315101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10657554 + 10657555.

It is an arithmetic number, because the mean of its divisors is an integer number (10657555).

Almost surely, 2^21315109 is an apocalyptic number.

It is an amenable number.

21315109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21315109 is an equidigital number, since it uses as much as digits as its factorization.

21315109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 270, while the sum is 22.

The square root of 21315109 is about 4616.8288900500. The cubic root of 21315109 is about 277.2655119473.

The spelling of 21315109 in words is "twenty-one million, three hundred fifteen thousand, one hundred nine".