21997494 has 20 divisors (see below), whose sum is σ = 49291044. Its totient is φ = 7332444.

The previous prime is 21997487. The next prime is 21997513. The reversal of 21997494 is 49479912.

It is a happy number.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 67732 + ... + 68055.

Almost surely, 2^21997494 is an apocalyptic number.

21997494 is an abundant number, since it is smaller than the sum of its proper divisors (27293550).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21997494 is a wasteful number, since it uses less digits than its factorization.

21997494 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135801 (or 135792 counting only the distinct ones).

The product of its digits is 163296, while the sum is 45.

The square root of 21997494 is about 4690.1486117180. The cubic root of 21997494 is about 280.1932934031.

It can be divided in two parts, 2199749 and 4, that added together give a triangular number (2199753 = T₂₀₉₇).

The spelling of 21997494 in words is "twenty-one million, nine hundred ninety-seven thousand, four hundred ninety-four".