21146021 has 4 divisors (see below), whose sum is σ = 22772652. Its totient is φ = 19519392.

The previous prime is 21145991. The next prime is 21146023. The reversal of 21146021 is 12064112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1653796 + 19492225 = 1286^2 + 4415^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21146021 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 (21146023) 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 3 ways as a sum of consecutive naturals, for example, 813296 + ... + 813321.

It is an arithmetic number, because the mean of its divisors is an integer number (5693163).

Almost surely, 2^21146021 is an apocalyptic number.

It is an amenable number.

21146021 is a deficient number, since it is larger than the sum of its proper divisors (1626631).

21146021 is a wasteful number, since it uses less digits than its factorization.

21146021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1626630.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 21146021 is about 4598.4802924445. The cubic root of 21146021 is about 276.5304028908.

The spelling of 21146021 in words is "twenty-one million, one hundred forty-six thousand, twenty-one".