20978537 has 4 divisors (see below), whose sum is σ = 21655296. Its totient is φ = 20301780.

The previous prime is 20978533. The next prime is 20978549. The reversal of 20978537 is 73587902.

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.

It is a cyclic number.

It is not a de Polignac number, because 20978537 - 2² = 20978533 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20978494 and 20978503.

It is not an unprimeable number, because it can be changed into a prime (20978533) 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, 338333 + ... + 338394.

It is an arithmetic number, because the mean of its divisors is an integer number (5413824).

Almost surely, 2^20978537 is an apocalyptic number.

It is an amenable number.

20978537 is a deficient number, since it is larger than the sum of its proper divisors (676759).

20978537 is an equidigital number, since it uses as much as digits as its factorization.

20978537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 676758.

The product of its (nonzero) digits is 105840, while the sum is 41.

The square root of 20978537 is about 4580.2332910017. The cubic root of 20978537 is about 275.7983938691.

The spelling of 20978537 in words is "twenty million, nine hundred seventy-eight thousand, five hundred thirty-seven".