21720746401 has 4 divisors (see below), whose sum is σ = 22863943600. Its totient is φ = 20577549204.

The previous prime is 21720746339. The next prime is 21720746407. The reversal of 21720746401 is 10464702712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21720746401 - 2¹³ = 21720738209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21720746407) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 571598571 + ... + 571598608.

It is an arithmetic number, because the mean of its divisors is an integer number (5715985900).

Almost surely, 2^21720746401 is an apocalyptic number.

It is an amenable number.

21720746401 is a deficient number, since it is larger than the sum of its proper divisors (1143197199).

21720746401 is a wasteful number, since it uses less digits than its factorization.

21720746401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1143197198.

The product of its (nonzero) digits is 18816, while the sum is 34.

The spelling of 21720746401 in words is "twenty-one billion, seven hundred twenty million, seven hundred forty-six thousand, four hundred one".