21400997 has 2 divisors, whose sum is σ = 21400998. Its totient is φ = 21400996.

The previous prime is 21400979. The next prime is 21401047. The reversal of 21400997 is 79900412.

Together with previous prime (21400979) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21215236 + 185761 = 4606^2 + 431^2 .

It is a cyclic number.

It is not a de Polignac number, because 21400997 - 2¹² = 21396901 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21400937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10700498 + 10700499.

It is an arithmetic number, because the mean of its divisors is an integer number (10700499).

Almost surely, 2^21400997 is an apocalyptic number.

It is an amenable number.

21400997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21400997 is an equidigital number, since it uses as much as digits as its factorization.

21400997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 21400997 is about 4626.1211614051. The cubic root of 21400997 is about 277.6374213174.

The spelling of 21400997 in words is "twenty-one million, four hundred thousand, nine hundred ninety-seven".