21246921 has 32 divisors (see below), whose sum is σ = 33600000. Its totient is φ = 13230864.

The previous prime is 21246913. The next prime is 21246931. The reversal of 21246921 is 12964212.

It is not a de Polignac number, because 21246921 - 2³ = 21246913 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21246931) 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 31 ways as a sum of consecutive naturals, for example, 42330 + ... + 42828.

It is an arithmetic number, because the mean of its divisors is an integer number (1050000).

Almost surely, 2^21246921 is an apocalyptic number.

It is an amenable number.

21246921 is a deficient number, since it is larger than the sum of its proper divisors (12353079).

21246921 is a wasteful number, since it uses less digits than its factorization.

21246921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 610 (or 604 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21246921 is about 4609.4382521084. The cubic root of 21246921 is about 276.9695344600.

It can be divided in two parts, 2124 and 6921, that added together give a triangular number (9045 = T₁₃₄).

The spelling of 21246921 in words is "twenty-one million, two hundred forty-six thousand, nine hundred twenty-one".