21273731 has 4 divisors (see below), whose sum is σ = 21484464. Its totient is φ = 21063000.

The previous prime is 21273713. The next prime is 21273737. The reversal of 21273731 is 13737212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21273731 - 2¹⁰ = 21272707 is a prime.

It is a super-2 number, since 2×21273731² = 905143261320722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21273731.

It is not an unprimeable number, because it can be changed into a prime (21273737) 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, 105215 + ... + 105416.

It is an arithmetic number, because the mean of its divisors is an integer number (5371116).

Almost surely, 2^21273731 is an apocalyptic number.

21273731 is a deficient number, since it is larger than the sum of its proper divisors (210733).

21273731 is a wasteful number, since it uses less digits than its factorization.

21273731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210732.

The product of its digits is 1764, while the sum is 26.

The square root of 21273731 is about 4612.3454987674. The cubic root of 21273731 is about 277.0859816406.

The spelling of 21273731 in words is "twenty-one million, two hundred seventy-three thousand, seven hundred thirty-one".