21215101 has 2 divisors, whose sum is σ = 21215102. Its totient is φ = 21215100.

The previous prime is 21215083. The next prime is 21215107. The reversal of 21215101 is 10151212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19589476 + 1625625 = 4426^2 + 1275^2 .

It is a cyclic number.

It is not a de Polignac number, because 21215101 - 2⁵ = 21215069 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21215107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607550 + 10607551.

It is an arithmetic number, because the mean of its divisors is an integer number (10607551).

Almost surely, 2^21215101 is an apocalyptic number.

It is an amenable number.

21215101 is a deficient number, since it is larger than the sum of its proper divisors (1).

21215101 is an equidigital number, since it uses as much as digits as its factorization.

21215101 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 21215101 is about 4605.9853451786. The cubic root of 21215101 is about 276.8311995318.

Adding to 21215101 its reverse (10151212), we get a palindrome (31366313).

It can be divided in two parts, 21215 and 101, that added together give a square (21316 = 146²).

The spelling of 21215101 in words is "twenty-one million, two hundred fifteen thousand, one hundred one".