21362821 has 16 divisors (see below), whose sum is σ = 23515200. Its totient is φ = 19329408.

The previous prime is 21362753. The next prime is 21362827. The reversal of 21362821 is 12826312.

It is a cyclic number.

It is not a de Polignac number, because 21362821 - 2²¹ = 19265669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21362827) 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, 75346 + ... + 75628.

It is an arithmetic number, because the mean of its divisors is an integer number (1469700).

Almost surely, 2^21362821 is an apocalyptic number.

It is an amenable number.

21362821 is a deficient number, since it is larger than the sum of its proper divisors (2152379).

21362821 is a wasteful number, since it uses less digits than its factorization.

21362821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468.

The product of its digits is 1152, while the sum is 25.

The square root of 21362821 is about 4621.9931847635. The cubic root of 21362821 is about 277.4722359475.

It can be divided in two parts, 2136 and 2821, that multiplied together give a triangular number (6025656 = T₃₄₇₁).

The spelling of 21362821 in words is "twenty-one million, three hundred sixty-two thousand, eight hundred twenty-one".