21051261 has 48 divisors (see below), whose sum is σ = 38982528. Its totient is φ = 10627200.

The previous prime is 21051257. The next prime is 21051271. The reversal of 21051261 is 16215012.

It is not a de Polignac number, because 21051261 - 2² = 21051257 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051241) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 25231 + ... + 26051.

It is an arithmetic number, because the mean of its divisors is an integer number (812136).

Almost surely, 2^21051261 is an apocalyptic number.

21051261 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21051261 is a deficient number, since it is larger than the sum of its proper divisors (17931267).

21051261 is a wasteful number, since it uses less digits than its factorization.

21051261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 882 (or 879 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21051261 is about 4588.1653196022. The cubic root of 21051261 is about 276.1167196937.

Adding to 21051261 its reverse (16215012), we get a palindrome (37266273).

It can be divided in two parts, 21051 and 261, that added together give a palindrome (21312).

The spelling of 21051261 in words is "twenty-one million, fifty-one thousand, two hundred sixty-one".