21953691 has 12 divisors (see below), whose sum is σ = 32568432. Its totient is φ = 14240016.

The previous prime is 21953677. The next prime is 21953741. The reversal of 21953691 is 19635912.

It is not a de Polignac number, because 21953691 - 2⁷ = 21953563 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21953621) 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, 32631 + ... + 33296.

It is an arithmetic number, because the mean of its divisors is an integer number (2714036).

Almost surely, 2^21953691 is an apocalyptic number.

21953691 is a deficient number, since it is larger than the sum of its proper divisors (10614741).

21953691 is a wasteful number, since it uses less digits than its factorization.

21953691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65970 (or 65967 counting only the distinct ones).

The product of its digits is 14580, while the sum is 36.

The square root of 21953691 is about 4685.4766032923. The cubic root of 21953691 is about 280.0071894412.

It can be divided in two parts, 2195 and 3691, that added together give a triangular number (5886 = T₁₀₈).

The spelling of 21953691 in words is "twenty-one million, nine hundred fifty-three thousand, six hundred ninety-one".