21261051 has 36 divisors (see below), whose sum is σ = 36718032. Its totient is φ = 11811744.

The previous prime is 21261041. The next prime is 21261059. The reversal of 21261051 is 15016212.

21261051 is a `hidden beast` number, since 2 + 1 + 2 + 610 + 51 = 666.

It is not a de Polignac number, because 21261051 - 2¹⁹ = 20736763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21261059) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 15666 + ... + 16968.

Almost surely, 2^21261051 is an apocalyptic number.

21261051 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21261051 is a deficient number, since it is larger than the sum of its proper divisors (15456981).

21261051 is a wasteful number, since it uses less digits than its factorization.

21261051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1360 (or 1350 counting only the distinct ones).

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

The square root of 21261051 is about 4610.9707220931. The cubic root of 21261051 is about 277.0309192332.

Adding to 21261051 its reverse (15016212), we get a palindrome (36277263).

The spelling of 21261051 in words is "twenty-one million, two hundred sixty-one thousand, fifty-one".