21261651 has 12 divisors (see below), whose sum is σ = 29031048. Its totient is φ = 13841184.

The previous prime is 21261631. The next prime is 21261659. The reversal of 21261651 is 15616212.

It is not a de Polignac number, because 21261651 - 2¹¹ = 21259603 is a prime.

It is a super-3 number, since 3×21261651³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21261659) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3631 + ... + 7463.

It is an arithmetic number, because the mean of its divisors is an integer number (2419254).

Almost surely, 2^21261651 is an apocalyptic number.

21261651 is a deficient number, since it is larger than the sum of its proper divisors (7769397).

21261651 is an equidigital number, since it uses as much as digits as its factorization.

21261651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3922 (or 3879 counting only the distinct ones).

The product of its digits is 720, while the sum is 24.

The square root of 21261651 is about 4611.0357838559. The cubic root of 21261651 is about 277.0335252033.

Adding to 21261651 its reverse (15616212), we get a palindrome (36877863).

It can be divided in two parts, 21261 and 651, that added together give a palindrome (21912).

The spelling of 21261651 in words is "twenty-one million, two hundred sixty-one thousand, six hundred fifty-one".