21215275 has 6 divisors (see below), whose sum is σ = 26306972. Its totient is φ = 16972200.

The previous prime is 21215263. The next prime is 21215287. The reversal of 21215275 is 57251212.

It is an interprime number because it is at equal distance from previous prime (21215263) and next prime (21215287).

It is not a de Polignac number, because 21215275 - 2⁷ = 21215147 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25), and also a Moran number because the ratio is a prime number: 848611 = 21215275 / (2 + 1 + 2 + 1 + 5 + 2 + 7 + 5).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 424281 + ... + 424330.

Almost surely, 2^21215275 is an apocalyptic number.

21215275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21215275 is a deficient number, since it is larger than the sum of its proper divisors (5091697).

21215275 is an equidigital number, since it uses as much as digits as its factorization.

21215275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 848621 (or 848616 counting only the distinct ones).

The product of its digits is 1400, while the sum is 25.

The square root of 21215275 is about 4606.0042336064. The cubic root of 21215275 is about 276.8319563590.

Adding to 21215275 its reverse (57251212), we get a palindrome (78466487).

It can be divided in two parts, 2121 and 5275, that added together give a square (7396 = 86²).

The spelling of 21215275 in words is "twenty-one million, two hundred fifteen thousand, two hundred seventy-five".