21240051 has 8 divisors (see below), whose sum is σ = 32365824. Its totient is φ = 12137160.

The previous prime is 21240049. The next prime is 21240073. The reversal of 21240051 is 15004212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21240051 - 2¹ = 21240049 is a prime.

It is a super-2 number, since 2×21240051² = 902279532965202, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21240051.

It is not an unprimeable number, because it can be changed into a prime (21240001) 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 7 ways as a sum of consecutive naturals, for example, 505695 + ... + 505736.

It is an arithmetic number, because the mean of its divisors is an integer number (4045728).

Almost surely, 2^21240051 is an apocalyptic number.

21240051 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21240051 is a deficient number, since it is larger than the sum of its proper divisors (11125773).

21240051 is a wasteful number, since it uses less digits than its factorization.

21240051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1011441.

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21240051 is about 4608.6929817466. The cubic root of 21240051 is about 276.9396793762.

Adding to 21240051 its reverse (15004212), we get a palindrome (36244263).

The spelling of 21240051 in words is "twenty-one million, two hundred forty thousand, fifty-one".