21253550 has 12 divisors (see below), whose sum is σ = 39531696. Its totient is φ = 8501400.

The previous prime is 21253543. The next prime is 21253591. The reversal of 21253550 is 5535212.

It is a congruent 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, 212486 + ... + 212585.

It is an arithmetic number, because the mean of its divisors is an integer number (3294308).

Almost surely, 2^21253550 is an apocalyptic number.

21253550 is a deficient number, since it is larger than the sum of its proper divisors (18278146).

21253550 is a wasteful number, since it uses less digits than its factorization.

21253550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 425083 (or 425078 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 21253550 is about 4610.1572641288. The cubic root of 21253550 is about 276.9983361254.

Adding to 21253550 its reverse (5535212), we get a palindrome (26788762).

The spelling of 21253550 in words is "twenty-one million, two hundred fifty-three thousand, five hundred fifty".