21695761 has 2 divisors, whose sum is σ = 21695762. Its totient is φ = 21695760.

The previous prime is 21695749. The next prime is 21695767. The reversal of 21695761 is 16759612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13395600 + 8300161 = 3660^2 + 2881^2 .

It is a cyclic number.

It is not a de Polignac number, because 21695761 - 2¹¹ = 21693713 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21695761.

It is not a weakly prime, because it can be changed into another prime (21695767) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10847880 + 10847881.

It is an arithmetic number, because the mean of its divisors is an integer number (10847881).

Almost surely, 2^21695761 is an apocalyptic number.

It is an amenable number.

21695761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21695761 is an equidigital number, since it uses as much as digits as its factorization.

21695761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 37.

The square root of 21695761 is about 4657.8708655350. The cubic root of 21695761 is about 278.9062818197.

The spelling of 21695761 in words is "twenty-one million, six hundred ninety-five thousand, seven hundred sixty-one".