21251066 has 4 divisors (see below), whose sum is σ = 31876602. Its totient is φ = 10625532.

The previous prime is 21251053. The next prime is 21251077. The reversal of 21251066 is 66015212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 18309841 + 2941225 = 4279^2 + 1715^2 .

It is a super-2 number, since 2×21251066² = 903215612272712, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5312765 + ... + 5312768.

Almost surely, 2^21251066 is an apocalyptic number.

21251066 is a deficient number, since it is larger than the sum of its proper divisors (10625536).

21251066 is a wasteful number, since it uses less digits than its factorization.

21251066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10625535.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21251066 is about 4609.8878511304. The cubic root of 21251066 is about 276.9875443491.

Adding to 21251066 its reverse (66015212), we get a palindrome (87266278).

The spelling of 21251066 in words is "twenty-one million, two hundred fifty-one thousand, sixty-six".