20507721 has 8 divisors (see below), whose sum is σ = 29447040. Its totient is φ = 12620112.

The previous prime is 20507717. The next prime is 20507737. The reversal of 20507721 is 12770502.

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

It is not a de Polignac number, because 20507721 - 2² = 20507717 is a prime.

It is a super-2 number, since 2×20507721² = 841133241227682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20507691 and 20507700.

It is not an unprimeable number, because it can be changed into a prime (20507701) 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, 262881 + ... + 262958.

It is an arithmetic number, because the mean of its divisors is an integer number (3680880).

Almost surely, 2^20507721 is an apocalyptic number.

It is an amenable number.

20507721 is a deficient number, since it is larger than the sum of its proper divisors (8939319).

20507721 is a wasteful number, since it uses less digits than its factorization.

20507721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 525855.

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 20507721 is about 4528.5451306131. The cubic root of 20507721 is about 273.7195391557.

The spelling of 20507721 in words is "twenty million, five hundred seven thousand, seven hundred twenty-one".