20942731 has 4 divisors (see below), whose sum is σ = 22045000. Its totient is φ = 19840464.

The previous prime is 20942723. The next prime is 20942741. The reversal of 20942731 is 13724902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13724902 = 2 ⋅6862451.

It is a cyclic number.

It is not a de Polignac number, because 20942731 - 2³ = 20942723 is a prime.

It is a super-2 number, since 2×20942731² = 877195963476722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20942731.

It is not an unprimeable number, because it can be changed into a prime (20942711) 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, 551106 + ... + 551143.

It is an arithmetic number, because the mean of its divisors is an integer number (5511250).

Almost surely, 2^20942731 is an apocalyptic number.

20942731 is a deficient number, since it is larger than the sum of its proper divisors (1102269).

20942731 is a wasteful number, since it uses less digits than its factorization.

20942731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1102268.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 20942731 is about 4576.3228688544. The cubic root of 20942731 is about 275.6413943454.

The spelling of 20942731 in words is "twenty million, nine hundred forty-two thousand, seven hundred thirty-one".