21497717641 has 9 divisors (see below), whose sum is σ = 21663339789. Its totient is φ = 21333355500.

The previous prime is 21497717629. The next prime is 21497717651. The reversal of 21497717641 is 14671779412.

The square root of 21497717641 is 146621.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 21497717641 - 2¹³ = 21497709449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21497717611) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 22139286 + ... + 22140256.

Almost surely, 2^21497717641 is an apocalyptic number.

21497717641 is the 146621-st square number.

21497717641 is the 73311-st centered octagonal number.

It is an amenable number.

21497717641 is a deficient number, since it is larger than the sum of its proper divisors (165622148).

21497717641 is an frugal number, since it uses more digits than its factorization.

21497717641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2244 (or 1122 counting only the distinct ones).

The product of its digits is 592704, while the sum is 49.

Multiplying 21497717641 by its sum of digits (49), we get a square (1053388164409 = 1026347²).

The spelling of 21497717641 in words is "twenty-one billion, four hundred ninety-seven million, seven hundred seventeen thousand, six hundred forty-one".