21969591 has 24 divisors (see below), whose sum is σ = 34429824. Its totient is φ = 12423600.

The previous prime is 21969589. The next prime is 21969631. The reversal of 21969591 is 19596912.

It is a happy number.

It is not a de Polignac number, because 21969591 - 2¹ = 21969589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21969511) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14416 + ... + 15866.

It is an arithmetic number, because the mean of its divisors is an integer number (1434576).

Almost surely, 2^21969591 is an apocalyptic number.

21969591 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21969591 is a deficient number, since it is larger than the sum of its proper divisors (12460233).

21969591 is a wasteful number, since it uses less digits than its factorization.

21969591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1571 (or 1564 counting only the distinct ones).

The product of its digits is 43740, while the sum is 42.

The square root of 21969591 is about 4687.1730285962. The cubic root of 21969591 is about 280.0747716977.

The spelling of 21969591 in words is "twenty-one million, nine hundred sixty-nine thousand, five hundred ninety-one".