20947916761 has 4 divisors (see below), whose sum is σ = 21143691792. Its totient is φ = 20752141732.

The previous prime is 20947916621. The next prime is 20947916777. The reversal of 20947916761 is 16761974902.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16761974902 = 2 ⋅8380987451.

It is a cyclic number.

It is not a de Polignac number, because 20947916761 - 2¹⁵ = 20947883993 is a prime.

It is a super-2 number, since 2×20947916761² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20947916699 and 20947916708.

It is not an unprimeable number, because it can be changed into a prime (20947913761) 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, 97887355 + ... + 97887568.

It is an arithmetic number, because the mean of its divisors is an integer number (5285922948).

Almost surely, 2^20947916761 is an apocalyptic number.

It is an amenable number.

20947916761 is a deficient number, since it is larger than the sum of its proper divisors (195775031).

20947916761 is a wasteful number, since it uses less digits than its factorization.

20947916761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195775030.

The product of its (nonzero) digits is 1143072, while the sum is 52.

The spelling of 20947916761 in words is "twenty billion, nine hundred forty-seven million, nine hundred sixteen thousand, seven hundred sixty-one".