21697761 has 16 divisors (see below), whose sum is σ = 29650880. Its totient is φ = 14109120.

The previous prime is 21697751. The next prime is 21697787. The reversal of 21697761 is 16779612.

It is not a de Polignac number, because 21697761 - 2⁷ = 21697633 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21697721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25011 + ... + 25863.

It is an arithmetic number, because the mean of its divisors is an integer number (1853180).

Almost surely, 2^21697761 is an apocalyptic number.

It is an amenable number.

21697761 is a deficient number, since it is larger than the sum of its proper divisors (7953119).

21697761 is a wasteful number, since it uses less digits than its factorization.

21697761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1056.

The product of its digits is 31752, while the sum is 39.

The square root of 21697761 is about 4658.0855509533. The cubic root of 21697761 is about 278.9148517798.

The spelling of 21697761 in words is "twenty-one million, six hundred ninety-seven thousand, seven hundred sixty-one".