21001550 has 24 divisors (see below), whose sum is σ = 39339000. Its totient is φ = 8341280.

The previous prime is 21001549. The next prime is 21001559. The reversal of 21001550 is 5510012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001559) by changing a digit.

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, 6041 + ... + 8859.

It is an arithmetic number, because the mean of its divisors is an integer number (1639125).

Almost surely, 2^21001550 is an apocalyptic number.

21001550 is a deficient number, since it is larger than the sum of its proper divisors (18337450).

21001550 is a wasteful number, since it uses less digits than its factorization.

21001550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2980 (or 2975 counting only the distinct ones).

The product of its (nonzero) digits is 50, while the sum is 14.

The square root of 21001550 is about 4582.7448107002. The cubic root of 21001550 is about 275.8992053004.

Adding to 21001550 its reverse (5510012), we get a palindrome (26511562).

The spelling of 21001550 in words is "twenty-one million, one thousand, five hundred fifty".