21397261731 has 8 divisors (see below), whose sum is σ = 28534695504. Its totient is φ = 14262334560.

The previous prime is 21397261703. The next prime is 21397261733. The reversal of 21397261731 is 13716279312.

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

It is not a de Polignac number, because 21397261731 - 2¹⁰ = 21397260707 is a prime.

It is a super-2 number, since 2×21397261731² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21397261733) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 606640 + ... + 640941.

It is an arithmetic number, because the mean of its divisors is an integer number (3566836938).

Almost surely, 2^21397261731 is an apocalyptic number.

21397261731 is a deficient number, since it is larger than the sum of its proper divisors (7137433773).

21397261731 is a wasteful number, since it uses less digits than its factorization.

21397261731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1253301.

The product of its digits is 95256, while the sum is 42.

It can be divided in two parts, 21397 and 261731, that added together give a triangular number (283128 = T₇₅₂).

The spelling of 21397261731 in words is "twenty-one billion, three hundred ninety-seven million, two hundred sixty-one thousand, seven hundred thirty-one".