21001051 has 4 divisors (see below), whose sum is σ = 21010504. Its totient is φ = 20991600.

The previous prime is 21001049. The next prime is 21001081. The reversal of 21001051 is 15010012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21001051 - 2¹ = 21001049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 631 + ... + 6511.

It is an arithmetic number, because the mean of its divisors is an integer number (5252626).

Almost surely, 2^21001051 is an apocalyptic number.

21001051 is a deficient number, since it is larger than the sum of its proper divisors (9453).

21001051 is an equidigital number, since it uses as much as digits as its factorization.

21001051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9452.

The product of its (nonzero) digits is 10, while the sum is 10.

The square root of 21001051 is about 4582.6903670224. The cubic root of 21001051 is about 275.8970201475.

Adding to 21001051 its reverse (15010012), we get a palindrome (36011063).

The spelling of 21001051 in words is "twenty-one million, one thousand, fifty-one".