21011967 has 56 divisors (see below), whose sum is σ = 34888560. Its totient is φ = 12597120.

The previous prime is 21011959. The next prime is 21011981. The reversal of 21011967 is 76911012.

It is not a de Polignac number, because 21011967 - 2³ = 21011959 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21011967.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011917) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 512467 + ... + 512507.

It is an arithmetic number, because the mean of its divisors is an integer number (623010).

Almost surely, 2^21011967 is an apocalyptic number.

21011967 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21011967 is a deficient number, since it is larger than the sum of its proper divisors (13876593).

21011967 is an equidigital number, since it uses as much as digits as its factorization.

21011967 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115 (or 100 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 21011967 is about 4583.8812157385. The cubic root of 21011967 is about 275.9448141082.

Adding to 21011967 its reverse (76911012), we get a palindrome (97922979).

The spelling of 21011967 in words is "twenty-one million, eleven thousand, nine hundred sixty-seven".