21007550 has 24 divisors (see below), whose sum is σ = 39211776. Its totient is φ = 8373440.

The previous prime is 21007531. The next prime is 21007561. The reversal of 21007550 is 5570012.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18602 + ... + 19698.

It is an arithmetic number, because the mean of its divisors is an integer number (1633824).

Almost surely, 2^21007550 is an apocalyptic number.

21007550 is a deficient number, since it is larger than the sum of its proper divisors (18204226).

21007550 is a wasteful number, since it uses less digits than its factorization.

21007550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1492 (or 1487 counting only the distinct ones).

The product of its (nonzero) digits is 350, while the sum is 20.

The square root of 21007550 is about 4583.3993934633. The cubic root of 21007550 is about 275.9254769742.

Adding to 21007550 its reverse (5570012), we get a palindrome (26577562).

The spelling of 21007550 in words is "twenty-one million, seven thousand, five hundred fifty".