21999968 has 12 divisors (see below), whose sum is σ = 43312500. Its totient is φ = 10999968.

The previous prime is 21999917. The next prime is 21999973. The reversal of 21999968 is 86999912.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343718 + ... + 343781.

It is an arithmetic number, because the mean of its divisors is an integer number (3609375).

Almost surely, 2^21999968 is an apocalyptic number.

It is an amenable number.

21999968 is a deficient number, since it is larger than the sum of its proper divisors (21312532).

21999968 is an equidigital number, since it uses as much as digits as its factorization.

21999968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 687509 (or 687501 counting only the distinct ones).

The product of its digits is 629856, while the sum is 53.

The square root of 21999968 is about 4690.4123486107. The cubic root of 21999968 is about 280.2037972090.

It can be divided in two parts, 2199 and 9968, that added together give a cube (12167 = 23³).

The spelling of 21999968 in words is "twenty-one million, nine hundred ninety-nine thousand, nine hundred sixty-eight".