21911887 has 2 divisors, whose sum is σ = 21911888. Its totient is φ = 21911886.

The previous prime is 21911839. The next prime is 21911891. The reversal of 21911887 is 78811912.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21911887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21911837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10955943 + 10955944.

It is an arithmetic number, because the mean of its divisors is an integer number (10955944).

Almost surely, 2^21911887 is an apocalyptic number.

21911887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21911887 is an equidigital number, since it uses as much as digits as its factorization.

21911887 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8064, while the sum is 37.

The square root of 21911887 is about 4681.0134586433. The cubic root of 21911887 is about 279.8293475437.

The spelling of 21911887 in words is "twenty-one million, nine hundred eleven thousand, eight hundred eighty-seven".