21281001 has 16 divisors (see below), whose sum is σ = 33183744. Its totient is φ = 11877264.

The previous prime is 21280999. The next prime is 21281011. The reversal of 21281001 is 10018212.

It is not a de Polignac number, because 21281001 - 2¹ = 21280999 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21281011) 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, 10881 + ... + 12686.

It is an arithmetic number, because the mean of its divisors is an integer number (2073984).

Almost surely, 2^21281001 is an apocalyptic number.

21281001 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21281001 is a deficient number, since it is larger than the sum of its proper divisors (11902743).

21281001 is a wasteful number, since it uses less digits than its factorization.

21281001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23620.

The product of its (nonzero) digits is 32, while the sum is 15.

The square root of 21281001 is about 4613.1335337274. The cubic root of 21281001 is about 277.1175414653.

Adding to 21281001 its reverse (10018212), we get a palindrome (31299213).

The spelling of 21281001 in words is "twenty-one million, two hundred eighty-one thousand, one".