21276021 has 16 divisors (see below), whose sum is σ = 30666944. Its totient is φ = 13042944.

The previous prime is 21275983. The next prime is 21276023. The reversal of 21276021 is 12067212.

It is not a de Polignac number, because 21276021 - 2⁷ = 21275893 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21276023) 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, 11085 + ... + 12861.

It is an arithmetic number, because the mean of its divisors is an integer number (1916684).

Almost surely, 2^21276021 is an apocalyptic number.

It is an amenable number.

21276021 is a deficient number, since it is larger than the sum of its proper divisors (9390923).

21276021 is a wasteful number, since it uses less digits than its factorization.

With its predecessor (21276020) it forms an eRAP, since the sums of their prime factors are consecutive (2099 and 2100).

21276021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2100.

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 21276021 is about 4612.5937388849. The cubic root of 21276021 is about 277.0959235440.

The spelling of 21276021 in words is "twenty-one million, two hundred seventy-six thousand, twenty-one".