21249518478401 has 8 divisors (see below), whose sum is σ = 21599539446504. Its totient is φ = 20899551323520.

The previous prime is 21249518478371. The next prime is 21249518478431. The reversal of 21249518478401 is 10487481594212.

It is a Cunningham number, because it is equal to 4609720²+1.

It is an interprime number because it is at equal distance from previous prime (21249518478371) and next prime (21249518478431).

It can be written as a sum of positive squares in 4 ways, for example, as 1 + 21249518478400 = 1^2 + 4609720^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21249518478401 - 2⁶ = 21249518478337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21249518478431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12656666 + ... + 14236931.

It is an arithmetic number, because the mean of its divisors is an integer number (2699942430813).

Almost surely, 2^{21249518478401} is an apocalyptic number.

It is an amenable number.

21249518478401 is a deficient number, since it is larger than the sum of its proper divisors (350020968103).

21249518478401 is a wasteful number, since it uses less digits than its factorization.

21249518478401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26906611.

The product of its (nonzero) digits is 5160960, while the sum is 56.

The spelling of 21249518478401 in words is "twenty-one trillion, two hundred forty-nine billion, five hundred eighteen million, four hundred seventy-eight thousand, four hundred one".