21888961 has 2 divisors, whose sum is σ = 21888962. Its totient is φ = 21888960.

The previous prime is 21888953. The next prime is 21888973. The reversal of 21888961 is 16988812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21762225 + 126736 = 4665^2 + 356^2 .

It is a cyclic number.

It is not a de Polignac number, because 21888961 - 2³ = 21888953 is a prime.

It is a super-2 number, since 2×21888961² = 958253227319042, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21885961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10944480 + 10944481.

It is an arithmetic number, because the mean of its divisors is an integer number (10944481).

Almost surely, 2^21888961 is an apocalyptic number.

It is an amenable number.

21888961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21888961 is an equidigital number, since it uses as much as digits as its factorization.

21888961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 55296, while the sum is 43.

The square root of 21888961 is about 4678.5639890890. The cubic root of 21888961 is about 279.7317200725.

The spelling of 21888961 in words is "twenty-one million, eight hundred eighty-eight thousand, nine hundred sixty-one".