20991974 has 8 divisors (see below), whose sum is σ = 33340248. Its totient is φ = 9878560.

The previous prime is 20991967. The next prime is 20991977. The reversal of 20991974 is 47919902.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20991977) 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, 308672 + ... + 308739.

It is an arithmetic number, because the mean of its divisors is an integer number (4167531).

Almost surely, 2^20991974 is an apocalyptic number.

20991974 is a deficient number, since it is larger than the sum of its proper divisors (12348274).

20991974 is a wasteful number, since it uses less digits than its factorization.

20991974 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 617430.

The product of its (nonzero) digits is 40824, while the sum is 41.

The square root of 20991974 is about 4581.6999028745. The cubic root of 20991974 is about 275.8572653413.

The spelling of 20991974 in words is "twenty million, nine hundred ninety-one thousand, nine hundred seventy-four".