21021051 has 16 divisors (see below), whose sum is σ = 28782720. Its totient is φ = 13641600.

The previous prime is 21021047. The next prime is 21021053. The reversal of 21021051 is 15012012.

It is not a de Polignac number, because 21021051 - 2² = 21021047 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21021053) 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 15 ways as a sum of consecutive naturals, for example, 19476 + ... + 20526.

It is an arithmetic number, because the mean of its divisors is an integer number (1798920).

Almost surely, 2^21021051 is an apocalyptic number.

21021051 is a deficient number, since it is larger than the sum of its proper divisors (7761669).

21021051 is a wasteful number, since it uses less digits than its factorization.

21021051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1226.

The product of its (nonzero) digits is 20, while the sum is 12.

The square root of 21021051 is about 4584.8719720402. The cubic root of 21021051 is about 275.9845743322.

Adding to 21021051 its reverse (15012012), we get a palindrome (36033063).

The spelling of 21021051 in words is "twenty-one million, twenty-one thousand, fifty-one".