20497721 has 8 divisors (see below), whose sum is σ = 21053760. Its totient is φ = 19948752.

The previous prime is 20497717. The next prime is 20497811. The reversal of 20497721 is 12779402.

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 20497721 - 2² = 20497717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20497021) 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, 4391 + ... + 7763.

It is an arithmetic number, because the mean of its divisors is an integer number (2631720).

Almost surely, 2^20497721 is an apocalyptic number.

It is an amenable number.

20497721 is a deficient number, since it is larger than the sum of its proper divisors (556039).

20497721 is a wasteful number, since it uses less digits than its factorization.

20497721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3535.

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 20497721 is about 4527.4408886257. The cubic root of 20497721 is about 273.6750414367.

The spelling of 20497721 in words is "twenty million, four hundred ninety-seven thousand, seven hundred twenty-one".