21203397 has 8 divisors (see below), whose sum is σ = 31412480. Its totient is φ = 14135580.

The previous prime is 21203383. The next prime is 21203407. The reversal of 21203397 is 79330212.

It is not a de Polignac number, because 21203397 - 2⁸ = 21203141 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 785311 = 21203397 / (2 + 1 + 2 + 0 + 3 + 3 + 9 + 7).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21203397.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21203317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 392629 + ... + 392682.

It is an arithmetic number, because the mean of its divisors is an integer number (3926560).

Almost surely, 2^21203397 is an apocalyptic number.

21203397 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21203397 is a deficient number, since it is larger than the sum of its proper divisors (10209083).

21203397 is an equidigital number, since it uses as much as digits as its factorization.

21203397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 785320 (or 785314 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 21203397 is about 4604.7146491395. The cubic root of 21203397 is about 276.7802825244.

The spelling of 21203397 in words is "twenty-one million, two hundred three thousand, three hundred ninety-seven".