21721734 has 48 divisors (see below), whose sum is σ = 48669504. Its totient is φ = 6998400.

The previous prime is 21721727. The next prime is 21721741. The reversal of 21721734 is 43712712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21721727) and next prime (21721741).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21721698 and 21721707.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 80019 + ... + 80289.

It is an arithmetic number, because the mean of its divisors is an integer number (1013948).

Almost surely, 2^21721734 is an apocalyptic number.

21721734 is an abundant number, since it is smaller than the sum of its proper divisors (26947770).

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

21721734 is a wasteful number, since it uses less digits than its factorization.

21721734 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 413 (or 410 counting only the distinct ones).

The product of its digits is 2352, while the sum is 27.

The square root of 21721734 is about 4660.6581080358. The cubic root of 21721734 is about 279.0175346439.

The spelling of 21721734 in words is "twenty-one million, seven hundred twenty-one thousand, seven hundred thirty-four".