21029121 has 6 divisors (see below), whose sum is σ = 30375410. Its totient is φ = 14019408.

The previous prime is 21029111. The next prime is 21029131. The reversal of 21029121 is 12192012.

It is an interprime number because it is at equal distance from previous prime (21029111) and next prime (21029131).

It can be written as a sum of positive squares in only one way, i.e., 16769025 + 4260096 = 4095^2 + 2064^2 .

It is not a de Polignac number, because 21029121 - 2¹⁰ = 21028097 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21029094 and 21029103.

It is not an unprimeable number, because it can be changed into a prime (21029101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1168276 + ... + 1168293.

Almost surely, 2^21029121 is an apocalyptic number.

It is an amenable number.

21029121 is a deficient number, since it is larger than the sum of its proper divisors (9346289).

21029121 is a wasteful number, since it uses less digits than its factorization.

21029121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2336575 (or 2336572 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The square root of 21029121 is about 4585.7519557865. The cubic root of 21029121 is about 276.0198867208.

The spelling of 21029121 in words is "twenty-one million, twenty-nine thousand, one hundred twenty-one".