21234921 has 16 divisors (see below), whose sum is σ = 30124224. Its totient is φ = 13259264.

The previous prime is 21234877. The next prime is 21234923. The reversal of 21234921 is 12943212.

It is a cyclic number.

It is not a de Polignac number, because 21234921 - 2⁷ = 21234793 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21234891 and 21234900.

It is not an unprimeable number, because it can be changed into a prime (21234923) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10990 + ... + 12776.

It is an arithmetic number, because the mean of its divisors is an integer number (1882764).

Almost surely, 2^21234921 is an apocalyptic number.

It is an amenable number.

21234921 is a deficient number, since it is larger than the sum of its proper divisors (8889303).

21234921 is a wasteful number, since it uses less digits than its factorization.

21234921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2040.

The product of its digits is 864, while the sum is 24.

The square root of 21234921 is about 4608.1363912107. The cubic root of 21234921 is about 276.9173816433.

It can be divided in two parts, 21234 and 921, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21234921 in words is "twenty-one million, two hundred thirty-four thousand, nine hundred twenty-one".