20691725821 has 16 divisors (see below), whose sum is σ = 22899850624. Its totient is φ = 18572307264.

The previous prime is 20691725809. The next prime is 20691725849. The reversal of 20691725821 is 12852719602.

It is a cyclic number.

It is not a de Polignac number, because 20691725821 - 2⁹ = 20691725309 is a prime.

It is a super-3 number, since 3×20691725821³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20691735821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 816280 + ... + 841246.

It is an arithmetic number, because the mean of its divisors is an integer number (1431240664).

Almost surely, 2^20691725821 is an apocalyptic number.

It is an amenable number.

20691725821 is a deficient number, since it is larger than the sum of its proper divisors (2208124803).

20691725821 is a wasteful number, since it uses less digits than its factorization.

20691725821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26740.

The product of its (nonzero) digits is 120960, while the sum is 43.

The spelling of 20691725821 in words is "twenty billion, six hundred ninety-one million, seven hundred twenty-five thousand, eight hundred twenty-one".